id:A108261 - OEIS Search Results

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2nd order recursive series having the property that the product of any two adjacent terms is a triangular number, T(b) = b(b+1)/2 where b equals term a(n) of related series A108262.

+0
2

2, 3, 12, 65, 374, 2175, 12672, 73853, 430442, 2508795, 14622324, 85225145, 496728542, 2895146103, 16874148072, 98349742325 (list; graph; listen)

	OFFSET	`0,1`
	LINKS	`K. J. Ramsey, RecursiveSeriesProblem`
	FORMULA	`a(n) = 6a(n-1) - a(n-2) - 4` `a(n)=1+(1/8)sqrt(2)[3-2sqrt(2)]^n+(1/2)[3+2sqrt(2)]^n-(1/8)[3+2sqrt(2)]^nsqrt(2)+(1 /2)[3-2*sqrt(2)]^n, with n>=0 - Paolo P. Lava (ppl(AT)spl.at), Jun 25 2008`
	EXAMPLE	`a(7)=12672`
	CROSSREFS	`Cf. A108262.` `Sequence in context: A052183 A123899 A032133 this_sequence A013152 A012911 A099805` `Adjacent sequences: A108258 A108259 A108260 this_sequence A108262 A108263 A108264`
	KEYWORD	`nonn`
	AUTHOR	`Kenneth John Ramsey (RamseyKK2(AT)aol.com), May 29 2005`

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Last modified September 6 09:40 EDT 2008. Contains 143480 sequences.

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