A157537 Half the number of length n integer sequences with sum zero and sum of squares 50.

1, 3, 42, 310, 1965, 12621, 86828, 614664, 4137255, 24696507, 135776850, 704076594, 3499379975, 16814719845, 78438871176, 355384933088, 1560604589541, 6638708644299, 27407266803082, 110092581701214, 431253742334877

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,0,50)/2.

Crossrefs

Sequence in context: A229071 A220857 A340613 * A322893 A114943 A119577

Adjacent sequences: A157534 A157535 A157536 * A157538 A157539 A157540

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved