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 A091983 a(0) = 1, a(n) = 20*sigma[3](n). 0

%I

%S 1,20,180,560,1460,2520,5040,6880,11700,15140,22680,26640,40880,43960,

%T 61920,70560,93620,98280,136260,137200,183960,192640,239760,243360,

%U 327600,315020,395640,408800,502240,487800,635040,595840,748980,745920

%N a(0) = 1, a(n) = 20*sigma[3](n).

%C G.f. A(x) satisfies 0=f(A(x),A(x^2),A(x^4)) where f(u,v,w)=u^2+33v^2+256w^2-18uv+16uw-288vw+220(v-w). - _Michael Somos_, Jul 19 2004

%F a(n) = 20*A001158(n), n>=1. - _R. J. Mathar_, Mar 23 2019

%o (PARI) a(n)=if(n<1,n==0,20*sigma(n,3)) /* _Michael Somos_, Jul 19 2004 */

%K nonn

%O 0,2

%A _N. J. A. Sloane_, following a suggestion of John McKay, Mar 19 2004

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Last modified December 4 02:40 EST 2021. Contains 349469 sequences. (Running on oeis4.)