A157551 Half the number of length n integer sequences with sum zero and sum of squares 722.

1, 9, 114, 3810, 103185, 2729181, 69340908, 1835068068, 46949243445, 1072699180795, 22440539853666, 442180822802082, 8348531623530553, 152424934237053765, 2702148696449820840, 46523455154624265192

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,0,722)/2.

Crossrefs

Sequence in context: A362576 A356240 A379522 * A157570 A223499 A362774

Adjacent sequences: A157548 A157549 A157550 * A157552 A157553 A157554

Keyword

nonn

Author

R. H. Hardin, Mar 02 2009

Status

approved