1,1

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]}]]

Cf. A006054, A006053.

Sequence in context: A095169 A105703 A055453 this_sequence A143709 A010446 A112781

Adjacent sequences: A122496 A122497 A122498 this_sequence A122500 A122501 A122502

nonn

Roger Bagula and Gary Adamson (rlbagulatftn(AT)yahoo.com), Sep 15 2006

Edited by N. J. A. Sloane (njas(AT)research.att.com), Serp 17 2006