0,5

a(n) =floor[floor[n^2/4]^2/4] =A002620(A002620(n))). a(4n)=4n^4; a(4n+1)=n^2*(2n+1)^2; a(4n+2)=2n(n+1)(2n(n+1)+1); a(4n+3)=(n+1)^2*(2n+1)^2. a(2n)=A060494(2n); a(2n-1)=A060494(2n-1)-A011861(n).

G.f.: x^3(1+2x+2x^3+x^4)/((1-x)^5*(1+x)^3*(1+x^2)). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 09 2008]

a(9)=100 since the ninth quarter-square is 20 and the twentieth quarter-square is 100.

Cf. A008233 for an alternative approach.

Sequence in context: A075385 A048150 A066186 this_sequence A009909 A009910 A060494

Adjacent sequences: A059400 A059401 A059402 this_sequence A059404 A059405 A059406

easy,nonn

Henry Bottomley (se16(AT)btinternet.com), Mar 21 2001