A118717 Sum of two consecutive semiprimes.

10, 15, 19, 24, 29, 36, 43, 47, 51, 59, 67, 69, 73, 77, 85, 95, 100, 106, 112, 115, 120, 127, 134, 143, 151, 159, 167, 171, 173, 178, 184, 187, 189, 201, 217, 226, 233, 237, 240, 243, 245, 252, 262, 267, 275, 283, 285, 288, 291, 301, 313, 317, 320, 327, 335

Offset: 1

Author

Luc Stevens (lms022(AT)yahoo.com), May 21 2006

Keywords

• nonn

Links

• Zak Seidov, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358.

Programs

Mathematica

Total /@ Partition[Select[Range[50000], 2 == PrimeOmega[#] &], 2, 1] (* Zak Seidov, Jan 31 2017 *)

PARI

isA001358(n)= { local(f,fct,sumpo); if(n <4, return(0) ); f=factor(n); fct=(matsize(f))[1]; sumpo= sum(i=1,fct,f[i,2]); if ( sumpo != 2, return(0), return(1) ); }
{ oldn=0; for(n=4,200, if( isA001358(n)==1, if( oldn !=0, print1(oldn+n,", "); ); oldn=n; ); ); } \\ R. J. Mathar, May 23 2006

Formula

a(n) = A001358(n) + A001358(n+1).

Extensions

Corrected and extended by R. J. Mathar, May 23 2006

Edited by Ray Chandler, Oct 31 2010