A157578 Half the number of length n integer sequences with sum zero and sum of squares 4232.

1, 3, 150, 15210, 1639575, 123643611, 7614820759, 421492526271, 22902703731540, 1192049263269315, 60248523072916695, 2966823784716819963, 139916416171825355244, 6279781745619795030660, 269526833541639073889370

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,0,4232)/2.

Crossrefs

Sequence in context: A118840 A111816 A157555 * A137802 A100203 A287319

Adjacent sequences: A157575 A157576 A157577 * A157579 A157580 A157581

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved