A157590 Half the number of length n integer sequences with sum zero and sum of squares 6728.

1, 3, 186, 26130, 3296565, 312282243, 24263695547, 1693530847881, 116031418602660, 7614709044887230, 485263665372726339, 30129597082995141381, 1791597506670518058876, 101387984322685789268190

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,0,6728)/2.

Crossrefs

Sequence in context: A371153 A198701 A157561 * A157236 A058856 A158469

Adjacent sequences: A157587 A157588 A157589 * A157591 A157592 A157593

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved