id:A046175 - OEIS Search Results

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Indices of triangular numbers which are also pentagonal.

+0
3

0, 1, 20, 285, 3976, 55385, 771420, 10744501, 149651600, 2084377905, 29031639076, 404358569165, 5631988329240, 78443478040201, 1092576704233580, 15217630381229925, 211954248632985376, 2952141850480565345 (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) + 6; g.f.: (1+5x)/((1-x)(1-14x+x^2)) - Warut Roonguthai (warut822(AT)yahoo.com) Jan 05 2001` `a(n+1)=7a(n)+3+2(12a(n)^2+12a(n)+1)^0.5 - Richard Choulet (richardchoulet(AT)yahoo.fr), Sep 19 2007`
	CROSSREFS	`Cf. A014979, A046174.` `Cf. A001834 A046174 A014979.` `Adjacent sequences: A046172 A046173 A046174 this_sequence A046176 A046177 A046178` `Sequence in context: A017953 A016317 A021404 this_sequence A016314 A021164 A017918`
	KEYWORD	`nonn,easy`
	AUTHOR	`Eric Weisstein (eric(AT)weisstein.com)`

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Last modified October 13 02:37 EDT 2008. Contains 145008 sequences.

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