A157602 Half the number of length n integer sequences with sum zero and sum of squares 9800.

1, 9, 378, 39990, 6207435, 649615491, 61839617931, 5291171373321, 436429418237100, 34318546032095787, 2635382197485052125, 197482663359487272702, 14177933118661639661880, 968391907322785974064260

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,0,9800)/2.

Crossrefs

Sequence in context: A218714 A157567 A157593 * A124042 A297738 A225988

Adjacent sequences: A157599 A157600 A157601 * A157603 A157604 A157605

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved