A157565 Half the number of length n integer sequences with sum zero and sum of squares 2178.

1, 3, 198, 9310, 376485, 22631679, 1141749532, 52484724372, 2266995222285, 89935056097975, 3267564223225962, 110915350947910158, 3617265650971040159, 114705568549182973950, 3535047653641613917560, 105710505247924746059104

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,0,2178)/2.

Crossrefs

Sequence in context: A336250 A256407 A256406 * A157598 A023310 A054701

Adjacent sequences: A157562 A157563 A157564 * A157566 A157567 A157568

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved