id:A081619 - OEIS Search Results

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Numbers whose divisors can be arranged as equilateral triangle.

+0
2

1, 4, 9, 12, 18, 20, 25, 28, 32, 44, 45, 48, 49, 50, 52, 63, 68, 75, 76, 80, 92, 98, 99, 112, 116, 117, 121, 124, 144, 147, 148, 153, 162, 164, 169, 171, 172, 175, 176, 188, 207, 208, 212, 236, 242, 243, 244, 245, 261, 268, 272, 275, 279, 284, 289, 292, 304, 316 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`A000005(a(n))=A000217(m) for some m; A000005(A081620(n))=n*(n+1)/2.`
	EXAMPLE	`Divisors of n=48 arranged as triangle:` `.......... 1` `........ 2...3` `...... 4...6...8` `... 12..16..24..48, therefore 48 is a term.`
	CROSSREFS	`Adjacent sequences: A081616 A081617 A081618 this_sequence A081620 A081621 A081622` `Sequence in context: A047461 A089910 A059269 this_sequence A038109 A067259 A060687`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Mar 24 2003`

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Last modified May 16 23:01 EDT 2008. Contains 139884 sequences.

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