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Search: id:A075871
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A075871 Numbers n such that 13*n^2 + 1 is a square. +0
1
0, 180, 233640, 303264540, 393637139280, 510940703520900, 663200639532988920, 860833919173116097260, 1117361763886065161254560, 1450334708690193406192321620, 1882533334518107155172472208200 (list; graph; listen)
OFFSET

1,2

COMMENT

Lim_{n-> Inf.} a(n)/a(n-1) = 649 + 180*Sqrt(13).

LINKS

Tanya Khovanova, Recursive Sequences

FORMULA

a(n)=1298*a(n-1)-a(n-2), n>1. - Michael Somos, Oct 30 2002

a(n) = [(649+180*Sqrt(13))^n - (649-180*Sqrt(13))^n] / (2*Sqrt(13))

a(n) = 1297*(a(n-1)+a(n-2))-a(n-3). a(n) = 1299*(a(n-1)-a(n-2))+a(n-3). - Mohamed Bouhamida (bhmd95(AT)yahoo.fr), Sep 20 2006

G.f.: 180x^2/(1-1298x+x^2). [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 18 2008]

CROSSREFS

Sequence in context: A091033 A146530 A057867 this_sequence A074811 A036200 A157747

Adjacent sequences: A075868 A075869 A075870 this_sequence A075872 A075873 A075874

KEYWORD

nonn

AUTHOR

Gregory V. Richardson (omomom(AT)hotmail.com), Oct 16 2002

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Last modified December 8 08:31 EST 2009. Contains 170430 sequences.


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