A122499 Semiprimes in A006053.

4, 9, 14, 155, 2993, 9707, 184183, 331981, 1942071, 1263047761, 140390505643, 455845099957, 296452328830865, 32951342156444219, 2381929669709247097441, 9063289616192276216577361, 34485996673867704851362967681, 426068342298911680872493712146539, 117190394374593808526426397401539675762247

Offset

1,1

Links

Table of n, a(n) for n=1..19.

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

Intersection of A001358 and A006053.

Cf. A006054.

Sequence in context: A105703 A055453 A247013 * A350419 A143709 A010446

Adjacent sequences: A122496 A122497 A122498 * A122500 A122501 A122502

Keyword

nonn

Author

Roger L. Bagula and Gary W. Adamson, Sep 15 2006

Extensions

Edited by N. J. A. Sloane, Sep 17 2006

More terms from Amiram Eldar, Jun 06 2025

Status

approved