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a(n) is the number of terms in the expansion of (x-2y)*(x^2-2y^2)*(x^3-2y^3)*...*(x^n-2y^n).
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%I #3 Sep 15 2012 15:19:13

%S 2,4,7,11,13,21,28,35,42,53,65,74,87,102,117,133,150,168,188,207,228,

%T 251,273,298,323,348,375,404,433,463,494,526,559,592,627,664,701,739,

%U 778,817,858,901,944,988,1032,1079,1126,1174,1222,1273

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

%p A086795 := proc(n)

%p mul( x^i-2*y^i,i=1..n) ;

%p expand(%) ;

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

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

%Y Cf. A086781.

%K nonn

%O 1,1

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