OFFSET
2,2
LINKS
R. H. Hardin, Table of n, a(n) for n=2..50
Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1).
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,0,8)/2.
G.f.: x^2*(1-6*x+15*x^2-45*x^4+54*x^5+16*x^6)/(1-x)^9. - Colin Barker, Feb 22 2012
a(n) = n (n-1)(n^6-27 n^5+295 n^4-1473 n^3+3376 n^2-3036 n+1008)/1152. - Robert Israel, Apr 07 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, Mar 02 2009
STATUS
approved