A157545 Half the number of length n integer sequences with sum zero and sum of squares 338.

1, 9, 90, 1570, 32775, 596253, 10391500, 188323164, 3295910835, 51520770235, 737464758030, 9942564439314, 128439149539155, 1604475021960825, 19461485770566600, 229260099669952384, 2617537416673754961

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,0,338)/2.

Crossrefs

Sequence in context: A294813 A218118 A160569 * A274953 A157558 A157584

Adjacent sequences: A157542 A157543 A157544 * A157546 A157547 A157548

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved