A157568 Half the number of length n integer sequences with sum zero and sum of squares 2592.

1, 3, 54, 6710, 552975, 42285705, 2331601391, 101037868356, 4170874974720, 169800684016755, 6716524310262195, 256753303252023825, 9424676123728329646, 331044899193112524525, 11129765080736905244370, 360217055543666912443944

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,0,2592)/2.

Crossrefs

Sequence in context: A158103 A174579 A171739 * A156911 A214006 A154604

Adjacent sequences: A157565 A157566 A157567 * A157569 A157570 A157571

Keyword

nonn

Author

R. H. Hardin Mar 02 2009

Status

approved