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Search: id:A133285
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| A133285 |
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Indices of the centered 12-gonal numbers which are also 12-gonal number, or numbers X such that 120*X^2-120*X+36 is a square. |
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+0
1
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| 1, 12, 253, 5544, 121705, 2671956, 58661317, 1287877008, 28274632849, 620754045660, 13628314371661, 299202162130872, 6568819252507513, 144214821393034404, 3166157251394249365, 69511244709280451616
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OFFSET
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1,2
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FORMULA
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a(n+2)=22*a(n+1)-a(n)-10 ; a(n+1)=11*a(n)-5+(120*a(n)^2-120*a(n)+36)^0.5
a(n)=(1/2)+(1/4)*[11+2*sqrt(30)]^n+(1/20)*[11+2*sqrt(30)]^n*sqrt(30)+(1/4)*[11-2*sqrt(30)]^n -(1/20)*sqrt(30)*[11-2*sqrt(30)]^n, with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Aug 06 2008]
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CROSSREFS
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Sequence in context: A065583 A129585 A034672 this_sequence A113091 A053324 A138451
Adjacent sequences: A133282 A133283 A133284 this_sequence A133286 A133287 A133288
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KEYWORD
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nonn
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AUTHOR
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Richard Choulet (richardchoulet(AT)yahoo.fr), Oct 16 2007
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EXTENSIONS
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More terms from Paolo P. Lava (ppl(AT)spl.at), Aug 06 2008
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