A118717 - OEIS

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

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OFFSET

1,1

LINKS

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

FORMULA

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

MATHEMATICA

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

PROG

(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

CROSSREFS

Cf. A001358.

Sequence in context: A343550 A285176 A135363 * A181529 A232501 A138593

Adjacent sequences: A118714 A118715 A118716 * A118718 A118719 A118720

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

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

Edited by Ray Chandler, Oct 31 2010

STATUS

approved