A157574 Half the number of length n integer sequences with sum zero and sum of squares 3528.

1, 9, 162, 9030, 900315, 78905043, 5045283243, 254993728356, 12275288985060, 582690164112595, 26896406705910159, 1199420057394958074, 51363567523493108520, 2104956036291257002350, 82564460378872392399390

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,0,3528)/2.

Crossrefs

Sequence in context: A156273 A051232 A362900 * A077280 A297436 A041147

Adjacent sequences: A157571 A157572 A157573 * A157575 A157576 A157577

Keyword

nonn

Author

R. H. Hardin, Mar 02 2009

Status

approved