A157561 Half the number of length n integer sequences with sum zero and sum of squares 1682.

1, 3, 186, 8710, 366285, 14870583, 574288652, 23199133896, 906030228645, 31596296548135, 1008864177035154, 30341990819899122, 874376529563919655, 24366254356588107705, 659305049442735042120, 17325808811806633829408

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,0,1682)/2.

Crossrefs

Sequence in context: A203562 A371153 A198701 * A157590 A157236 A058856

Adjacent sequences: A157558 A157559 A157560 * A157562 A157563 A157564

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved