A157571 Half the number of length n integer sequences with sum zero and sum of squares 3042.

1, 9, 270, 10990, 622725, 43526469, 2629049500, 142957923228, 7300452572415, 342254197570615, 14695487432860410, 589524950365892190, 22721530823371062501, 851515705898338365990, 31013728074479042288280

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,0,3042)/2.

Crossrefs

Sequence in context: A168600 A088672 A300169 * A202689 A364438 A218693

Adjacent sequences: A157568 A157569 A157570 * A157572 A157573 A157574

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved