A157553 Half the number of length n integer sequences with sum zero and sum of squares 882.

1, 9, 162, 3010, 100035, 3757383, 119414988, 3493064772, 95851672965, 2417802179815, 55917688232274, 1207875284200806, 25067626930769059, 505877445756815265, 9921228112937485800, 188795923012791958280

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,0,882)/2.

Crossrefs

Sequence in context: A158749 A300843 A133681 * A202438 A237024 A156273

Adjacent sequences: A157550 A157551 A157552 * A157554 A157555 A157556

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved