id:A046174 - OEIS Search Results

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Indices of pentagonal numbers which are also triangular.

+0
3

0, 1, 12, 165, 2296, 31977, 445380, 6203341, 86401392, 1203416145, 16761424636, 233456528757, 3251629977960, 45289363162681, 630799454299572, 8785902997031325, 122371842504138976, 1704419892060914337 (list; graph; listen)

	OFFSET	`0,3`
	LINKS	`Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.`
	FORMULA	`a(n) = 14a(n-1) - a(n-2) - 2; g.f.: (1-3x)/((1-x)(1-14x+x^2)) - Warut Roonguthai (warut822(AT)yahoo.com) Jan 05 2001` `a(n+1)=7a(n)-1+2(12a(n)^2-4a(n)+1)^0.5 - Richard Choulet (richardchoulet(AT)yahoo.fr), Sep 19 2007`
	CROSSREFS	`Cf. A014979, A046175.` `Cf. A046175 A014979 A001834.` `Sequence in context: A138455 A024221 A093152 this_sequence A055760 A056591 A099745` `Adjacent sequences: A046171 A046172 A046173 this_sequence A046175 A046176 A046177`
	KEYWORD	`nonn,easy`
	AUTHOR	`Eric Weisstein (eric(AT)weisstein.com)`

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Last modified September 5 19:27 EDT 2008. Contains 143485 sequences.

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