A157546 Half the number of length n integer sequences with sum zero and sum of squares 392.

1, 9, 54, 1290, 47385, 1080891, 19941831, 335927439, 5541820740, 87714576070, 1349748111657, 20228679068676, 290345411571852, 3966279413712840, 51810189395306490, 652108043960695984, 7955418278826810531

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,0,392)/2.

Crossrefs

Sequence in context: A363415 A157539 A205814 * A157560 A157588 A270575

Adjacent sequences: A157543 A157544 A157545 * A157547 A157548 A157549

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved