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%I #21 Sep 08 2022 08:45:46
%S 1,3,6,9,12,15,17,18,18,17,15,12,9,6,3,1
%N Expansion of the polynomial (1-x^3) * (1-x^6) * (1-x^9) / (1-x)^3.
%C This is a row of the triangle A162499.
%C Only finitely many terms are nonzero.
%p m:=3: seq(coeff(series(mul((1-x^(3*i)),i=1..m)/(1-x)^m, x,n+1),x,n),n=0..16); # _Muniru A Asiru_, Jul 07 2018
%t CoefficientList[ Series[Times @@ (1 - x^(3 Range@3))/(1 - x)^3, {x, 0, 40}], x] (* _Wesley Ivan Hurt_, Sep 13 2014 and slightly modified by _Robert G. Wilson v_, Jul 23 2018 *)
%o (PARI) x='x+O('x^16); Vec((1-x^3)*(1-x^6)*(1-x^9)/(1-x)^3) \\ _G. C. Greubel_, Jul 06 2018
%o (Magma) m:=16; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((1-x^3)*(1-x^6)*(1-x^9)/(1-x)^3)); /* complete row without zeros */ // _G. C. Greubel_, Jul 06 2018
%Y Cf. A162499.
%K nonn,fini,full
%O 0,2
%A _N. J. A. Sloane_, Dec 02 2009