A136151 Composites n with exactly two distinct prime divisors and of the form n=1+(any prime).

6, 12, 14, 18, 20, 24, 38, 44, 48, 54, 62, 68, 72, 74, 80, 98, 104, 108, 152, 158, 164, 192, 194, 200, 212, 224, 242, 272, 278, 284, 314, 332, 338, 368, 384, 398, 422, 432, 458, 464, 488, 500, 524, 542, 548, 578, 608, 614, 632, 648, 662, 674, 692, 734, 752, 758

Offset: 1

Author

Enoch Haga, Dec 16 2007

Keywords

• easy
• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A136152, A136153, A136154, A136155.

Programs

Maple

isA136151 := proc(n) if isprime(n-1) then if nops(numtheory[factorset](n)) =2 then true; else false ; fi ; else false ; fi ; end: for i from 1 to 200 do n := ithprime(i)+1 ; if isA136151( n) then printf("%d, ",n) ; fi ; od: # R. J. Mathar, Feb 01 2008

Mathematica

Select[Range[800],PrimeNu[#]==2&&PrimeQ[#-1]&] (* Harvey P. Dale, Jun 22 2018 *)

Formula

A008864 INTERSECT A007774. - R. J. Mathar, Feb 01 2008

Extensions

Edited by R. J. Mathar, Feb 01 2008