A157567 Half the number of length n integer sequences with sum zero and sum of squares 2450.

1, 9, 378, 13330, 689715, 30934071, 1463659596, 72481823352, 3407856306435, 142400570465307, 5478965101306950, 198874787418398598, 6919440283487706065, 232730571288134765160, 7599816260357477794632, 241028324482889751669040

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,0,2450)/2.

Crossrefs

Sequence in context: A238561 A290574 A218714 * A157593 A157602 A124042

Adjacent sequences: A157564 A157565 A157566 * A157568 A157569 A157570

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved