id:A095202 - OEIS Search Results

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Value of largest k such that (n-1) + (n-2) + (n-3) + ... + (n-k) is a multiple of n, or 0 if no such k exists.

+0
3

0, 0, 2, 0, 4, 3, 6, 0, 8, 4, 10, 8, 12, 7, 14, 0, 16, 8, 18, 15, 20, 11, 22, 15, 24, 12, 26, 7, 28, 24, 30, 0, 32, 16, 34, 8, 36, 19, 38, 15, 40, 35, 42, 32, 44, 23, 46, 32, 48, 24, 50, 39, 52, 27, 54, 48, 56, 28, 58, 39, 60, 31, 62, 0, 64, 44, 66, 16, 68, 55, 70, 63, 72, 36, 74, 56 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Equivalently, largest k < n such that k-th triangular number (A000217(k)) is a multiple of n, or 0 if no such k exists.`
	FORMULA	`a(2n-1) = 2n-2 for all n >= 1; a(2^n) = 0 for all n >= 1.`
	PROGRAM	`(PARI) {a(n) = s=0; saved_k=0; k=0; while(k<n-1, k++; s=s+(n-k); if(s%n==0, saved_k=k)); saved_k}`
	CROSSREFS	`Cf. A095200, A095201.` `Cf. A000217 (triangular numbers).` `Adjacent sequences: A095199 A095200 A095201 this_sequence A095203 A095204 A095205` `Sequence in context: A122512 A128263 A140254 this_sequence A093443 A099092 A081236`
	KEYWORD	`nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jun 05 2004`
	EXTENSIONS	`Edited by Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jun 08 2004`

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Last modified October 13 09:05 EDT 2008. Contains 145008 sequences.

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