A173470 Semiprimes in A023037.

85, 781, 137257, 28531167061

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Feb 19 2010

Keywords

• nonn

Comments

The terms a(5) etc. have at least 63 digits (if they exist), so the pattern of terms does not continue as in A001039. [From R. J. Mathar, Feb 27 2010]

Programs

Mathematica

f1[n_]:=Module[{s=0},Do[s+=n^a,{a,0,n-1}];s]; f2[n_]:=Last/@FactorInteger[n]=={1,1}||Last/@FactorInteger[n]=={2}; Select[Table[f1[n],{n,50}],f2[ # ]&]