A157566 Half the number of length n integer sequences with sum zero and sum of squares 2312.

1, 3, 102, 8190, 665685, 36705753, 1679350127, 68733531189, 2760184991340, 106183264044550, 3966764429800029, 144378604643078598, 5032695166253713140, 166954292511159130110, 5296343179095984782250, 161894623559389026065130

Offset

2,2

Links

R. H. Hardin, Table of n, a(n) for n=2..50

Formula

[cache enabling] count(n,s,ss)->count(n,t,tt) where t=s mod n, q=(t-s)/n, tt=ss+2*q*s+n*q^2; count(n,t,tt)=sum[i^2<=tt]{ count(n-1,t-i,tt-i^2) }. a(n)=count(n,0,2312)/2.

Crossrefs

Sequence in context: A290027 A224817 A157549 * A364418 A157600 A139908

Adjacent sequences: A157563 A157564 A157565 * A157567 A157568 A157569

Keyword

nonn

Author

R. H. Hardin, Mar 02 2009

Status

approved