A157554 Half the number of length n integer sequences with sum zero and sum of squares 968.

1, 3, 66, 3990, 178335, 6510483, 190667659, 5047394427, 131071431060, 3262733109790, 78872812374741, 1857536871457917, 41896936373100900, 899337065318075790, 18460566561637223550, 365127965985604164628

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,0,968)/2.

Crossrefs

Sequence in context: A368596 A157984 A187547 * A185053 A165655 A157576

Adjacent sequences: A157551 A157552 A157553 * A157555 A157556 A157557

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved