A157581 Half the number of length n integer sequences with sum zero and sum of squares 4802.

1, 15, 390, 21010, 1806015, 123582921, 7932838172, 541388995092, 35637846633315, 2098170095389555, 113237331813959034, 5754386605886291022, 280189305372079613419, 13193562175797681608910, 603200922513642478421880

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,0,4802)/2.

Crossrefs

Sequence in context: A129615 A286139 A069990 * A143001 A250950 A366300

Adjacent sequences: A157578 A157579 A157580 * A157582 A157583 A157584

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved