OFFSET
1,1
COMMENTS
EXAMPLE
10 is a member because 10 is 4th semiprime and 4 is a semiprime.
MATHEMATICA
With[{sprs=Select[Range[700], PrimeOmega[#]==2&]}, Flatten[Table[Take[sprs, Take[ sprs, {n}]], {n, 60}]]] (* Harvey P. Dale, Aug 22 2011 *)
PROG
(PARI) A001358()= { local(resul); resul = [4]; for(n=5, 1000, if ( bigomega(n) == 2, resul =concat(resul, n); ); ); return(resul); } { spr=Vec(A001358()); sprlen=(matsize(spr))[2]; for(n=1, sprlen, if( spr[n]>=sprlen, break; ); print1(spr[spr[n]], ", "); ); } - R. J. Mathar, May 23 2006
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Feb 24 2004
STATUS
approved