A157549 Half the number of length n integer sequences with sum zero and sum of squares 578.

1, 3, 102, 2730, 73965, 1747893, 39747932, 941571576, 21552984495, 440593787755, 8246912787894, 145396398912414, 2456171567279885, 40123597587869565, 636426718791995640, 9804070912688974376, 146378210616014587821

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,0,578)/2.

Crossrefs

Sequence in context: A037062 A290027 A224817 * A157566 A364418 A157600

Adjacent sequences: A157546 A157547 A157548 * A157550 A157551 A157552

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved