A157572 Half the number of length n integer sequences with sum zero and sum of squares 3200.

1, 3, 42, 13330, 1149525, 68923281, 3762973571, 184036492377, 8678968080840, 390210773279547, 17118756925603575, 733096379424490302, 30076017737894907870, 1173815703627064565445, 43806372065182513944702

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,0,3200)/2.

Crossrefs

Sequence in context: A157552 A058808 A155210 * A332973 A137192 A253577

Adjacent sequences: A157569 A157570 A157571 * A157573 A157574 A157575

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved