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a(n) is the number of terms in the expansion of (x+y+z)*(x^2+y^2+z^2)*(x^3+y^3+z^3)*...*(x^n+y^n+z^n).
5

%I #5 Sep 04 2018 20:00:40

%S 3,9,24,60,130,247,429,697,1075,1590,2272,3154,4272,5665,7375,9447,

%T 11929,14872,18330,22360,27022,32379,38497,45445,53295,62122,72004,

%U 83022,95260,108805,123747,140179

%N a(n) is the number of terms in the expansion of (x+y+z)*(x^2+y^2+z^2)*(x^3+y^3+z^3)*...*(x^n+y^n+z^n).

%p A086796 := proc(n)

%p mul( x^i+y^i+z^i,i=1..n) ;

%p expand(%) ;

%p nops([coeffs(%)]) ;

%p end proc: # _R. J. Mathar_, Sep 15 2012

%t Table[Length[Expand[Times@@Table[Total[{x,y,z}^n],{n,m}]]],{m,40}] (* _Harvey P. Dale_, Sep 04 2018 *)

%Y Cf. A000124.

%K nonn

%O 1,1

%A Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 05 2003