A157539 Half the number of length n integer sequences with sum zero and sum of squares 98.

1, 9, 54, 430, 5265, 51471, 471996, 4601556, 43269345, 363940555, 2806131702, 20371562718, 141703205917, 953199973950, 6225689789880, 39490548010664, 242779946083425, 1445870078850825, 8356848826556090, 46996171775421630

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,0,98)/2.

Crossrefs

Sequence in context: A383198 A093847 A363415 * A205814 A157546 A157560

Adjacent sequences: A157536 A157537 A157538 * A157540 A157541 A157542

Keyword

nonn

Author

R. H. Hardin, Mar 02 2009

Status

approved