A157562 Half the number of length n integer sequences with sum zero and sum of squares 1800.

1, 3, 126, 6510, 336015, 19347993, 928126199, 34039360092, 1173329179500, 39563049010881, 1301454506052525, 41455087636231074, 1268529094022948940, 37131123353064641460, 1040240395936575811890, 28055696919876575091824

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,0,1800)/2.

Crossrefs

Sequence in context: A241647 A157547 A160879 * A324152 A274314 A157592

Adjacent sequences: A157559 A157560 A157561 * A157563 A157564 A157565

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved