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Semiprimes in A006053.
0

%I #5 Oct 12 2012 14:55:29

%S 4,9,14,155,2993,9707,184183,331981,1942071,1263047761,140390505643

%N Semiprimes in A006053.

%t SemiprimeQ[n_Integer] := Plus @@ (Last /@ FactorInteger[n]) == 2 a = Table[ SeriesCoefficient[ Series[x/(x^3 - 2*x^2 - x + 1), {x, 0, 50}], n], {n, 0, 50}] f[n_] = If[SemiprimeQ[a[[n]]] == True, a[[n]], {}] Flatten[Table[f[n], {n, 1, Length[a]}]]

%Y Cf. A006054, A006053.

%K nonn

%O 1,1

%A _Roger L. Bagula_ and _Gary W. Adamson_, Sep 15 2006

%E Edited by _N. J. A. Sloane_, Serp 17 2006