OFFSET
0,2
REFERENCES
Mentioned in a problem on p. 334 of Two-Year College Math. Jnl., Vol. 25, 1994.
LINKS
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
FORMULA
a(n)=sum(i=1, n, i^2)*sum(i=n+1, 2*n, i^2).
G.f.: x(4+97x+287x^2+159x^3+13x^4)/(1-x)^7.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michael Somos, Jul 27 2002
STATUS
approved