A157558 Half the number of length n integer sequences with sum zero and sum of squares 1352.

1, 9, 90, 4710, 294975, 12521313, 439040875, 13748247801, 422094067740, 12416563759270, 354721205123505, 9872974834469253, 263171856408106464, 6676220201317388190, 161958493217535635430, 3785772107967822217382

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,0,1352)/2.

Crossrefs

Sequence in context: A160569 A157545 A274953 * A157584 A077334 A020243

Adjacent sequences: A157555 A157556 A157557 * A157559 A157560 A157561

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved