A157548 Half the number of length n integer sequences with sum zero and sum of squares 512.

1, 3, 6, 1710, 70215, 1835001, 38831135, 747772191, 14106580920, 255318883105, 4489013718651, 76895304533697, 1261399140060514, 19692099463166235, 293975822555447490, 4228706577830551202, 58957940194082852859

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,0,512)/2.

Crossrefs

Sequence in context: A034879 A113588 A071106 * A134901 A157564 A122182

Adjacent sequences: A157545 A157546 A157547 * A157549 A157550 A157551

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved