id:A081295 - OEIS Search Results

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a(n) = (-1)^(n+1)* coefficient of x^n in sum(k>=1,x^k/(1+2*x^k)).

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1, 1, 5, 9, 17, 29, 65, 137, 261, 497, 1025, 2085, 4097, 8129, 16405, 32905, 65537, 130845, 262145, 524793, 1048645, 2096129, 4194305, 8390821, 16777233, 33550337, 67109125, 134225865, 268435457, 536855053, 1073741825, 2147516553 (list; graph; listen)

	OFFSET	`1,3`
	FORMULA	`a(p)=2^(p-1)-1 p prime.`
	PROGRAM	`(PARI) a(n)=if(n<1, 0, (-1)^(n+1)polcoeff(sum(k=1, n, x^k/(1+2x^k), x*O(x^n)), n))`
	CROSSREFS	`Cf. A034729.` `Adjacent sequences: A081292 A081293 A081294 this_sequence A081296 A081297 A081298` `Sequence in context: A080335 A089109 A100449 this_sequence A059743 A000322 A020737`
	KEYWORD	`nonn`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 20 2003`

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Last modified May 13 01:46 EDT 2008. Contains 139661 sequences.

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