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Topic: Tetrahedral number

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Centered triangular number

Figurate number

Sphere packing

Simplex

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	tetrahedral number
		In this case the total number of beads is (3rd triangular number) + (2nd triangular number) + (1st triangular number) = 6 + 3 + 1 = 10.
		In general the nth tetrahedral number is equal to the sum of the first n triangular numbers.
		This is the same as the 4th number from the left in the (n + 3)th row of Pascal's triangle.
	www.daviddarling.info /encyclopedia/T/tetrahedral_number.html (189 words)

	More about Palindromic Tetrahedrals
		The sum of two consecutive tetrahedral numbers is a square pyramidal number.
		Tetrahedral numbers which are sum of 2 tetrahedrals.
		Not the sum of 4 tetrahedrals (a finite sequence).
	www.worldofnumbers.com /tetra.htm (309 words)

	Tetrahedral numbers
		Tetrahedral numbers are pyramidal numbers and are the sum of consectuive triangular numbers.
		The first tetrahedral number is 1, the second is 4, the third is 10, the forth is 20, and so on.
		is referenced as the sequence of tetrahedral numbers :
	milan.milanovic.org /math/english/tetrahedral/tetrahedral.html (429 words)

	PlanetMath: tetrahedral number
		This means that tetrahedral numbers can be looked up in Pascal's triangle.
		Tetrahedral numbers have practical applications in sphere packing.
		This is version 3 of tetrahedral number, born on 2006-06-02, modified 2006-06-11.
	planetmath.org /encyclopedia/TetrahedralNumber.html (241 words)

	Contents
		Pentatope Numbers (4-tetrahedron numbers) can be found in the fifth column of Pascal`s triangle, which are of course the sum of the tetrahedral numbers....
		The connection between magic numbers on one side and pyramidal numbers and tetrahedral numbers and triangular numbers, on the other, is highly amusing...
		The Fibonacci numbers are therefore applicable to the growth of every living thing, including a single cell, a grain of wheat, a hive of bees, and even all of mankind.Fibonacci slides.
	milan.milanovic.org /math/english/contents.html (1810 words)

	20 (number) - Wikipedia, the free encyclopedia
		The number of proteinogenic amino acids that are encoded by the standard genetic code.
		The Saros number of the solar eclipse series which began on -2286 June 5 and ended on -1006 July 13.
		The number 20 is used as an index in measuring visual acuity.
	en.wikipedia.org /wiki/Twenty (701 words)

	Encyclopedia article: 1000 (number) (Site not responding. Last check: 2007-10-18)
		1000 is the natural number (The number 1 and any other number obtained by adding 1 to it repeatedly) following 999 (additional info and facts about 999) and preceding 1001 (additional info and facts about 1001).
		1330 - tetrahedral number;1331 - cube (A block in the (approximate) shape of a cube) of 11 (The cardinal number that is the sum of ten and one), centered heptagonal number
		1722 - Giuga number, pronic number;1728 - cube of 12 (The cardinal number that is the sum of eleven and one) and so is the number of cubic inch (A unit of length equal to one twelfth of a foot) es in a cubic foot (The foot of a human being)
	www.absoluteastronomy.com /encyclopedia/1/10/1000_(number).htm (2046 words)

	POLYHEDRAL NUMBERS - Online Information article about POLYHEDRAL NUMBERS
		Cubic numbers are 1, 8, 27, 64, 125, andc.; or generally n3.
		Octahedral numbers are r, 6, 19, 44, andc., or generally **n(2n2+I).
		Dodecahedral numbers are 1, 20, 84, 220, andc.; or generally 2n(9n'—9n+2).
	encyclopedia.jrank.org /PIG_POL/POLYHEDRAL_NUMBERS.html (424 words)

	Numbers: number 20
		A tetrahedral number - the sum of the first four triangular numbers.
		This was the number of households which had to be taxed to provide for one soldier.
		One person secretly writes down a number and the others ask questions like `Is it an even number?', `Is it more than a thousand?', `Does it have a 6 in it?'.
	richardphillips.org.uk /number/Num20.htm (408 words)

	Numbers: number 10
		A tetrahedral number - the sum of the first three triangular numbers.
		If a number ends with a zero it is exactly divisible by ten.
		We have ten digits on our hands, and ten is the base of our number system: the decimal system.
	richardphillips.org.uk /number/Num10.htm (543 words)

	ipedia.com: 2000 (number) Article (Site not responding. Last check: 2007-10-18)
		Two thousand (2000) is the natural number following 1999 and preceding 2001.
		Two thousand is the highest number expressible using only two unmodified characters in roman numerals (MM).
		In Star Trek, the registry number of the USS Excelsior, NX-2000 in Star Trek III: The Search for Spock, and NCC-2000 commanded by Hikaru Sulu in Star Trek VI: The Undiscovered Country.
	www.ipedia.com /2000__number_.html (141 words)

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