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Search: id:A077401
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A077401 Second member of Diophantine pair (m,k) that solves 7(m^2+m)=k^2+k; a(n)=k. +0
4
0, 6, 14, 104, 231, 1665, 3689, 26543, 58800, 423030, 937118, 6741944, 14935095, 107448081, 238024409, 1712427359, 3793455456, 27291389670, 60457262894, 434949807368, 963522750855, 6931905528225, 15355906750793 (list; graph; listen)
OFFSET

0,2

FORMULA

G.f.: x(6+8x-6x^2-x^3)/((1-x)(1-16x^2+x^4)).

a(n)=16*a(n-2)+a(n-4)+7, n>=4.

Let b(n) be A077400 then a(n)=(-1+sqrt(8*b(n)+1))/2.

PROGRAM

(PARI) a(n)=if(n<0, 0, polcoeff(x*(6+8*x-6*x^2-x^3)/((1-x)*(1-16*x^2+x^4))+x*O(x^n), n))

CROSSREFS

Cf. A077399, A077400. The m values are in A077398.

Sequence in context: A139257 A056842 A130263 this_sequence A158965 A013314 A019306

Adjacent sequences: A077398 A077399 A077400 this_sequence A077402 A077403 A077404

KEYWORD

nonn

AUTHOR

Bruce Corrigan (scentman(AT)myfamily.com), Nov 05 2002

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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