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A122499
Semiprimes in A006053.
0
4, 9, 14, 155, 2993, 9707, 184183, 331981, 1942071, 1263047761, 140390505643
OFFSET
1,1
MATHEMATICA
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]}]]
CROSSREFS
Sequence in context: A105703 A055453 A247013 * A350419 A143709 A010446
KEYWORD
nonn
AUTHOR
EXTENSIONS
Edited by N. J. A. Sloane, Serp 17 2006
STATUS
approved