A176548 Non-semiprimes whose reversal is a prime.

2, 3, 5, 7, 11, 13, 16, 17, 20, 30, 31, 32, 37, 50, 70, 71, 73, 76, 79, 92, 97, 98, 101, 104, 107, 110, 112, 113, 124, 125, 128, 130, 131, 136, 140, 149, 151, 152, 157, 160, 164, 167, 170, 172, 175, 179, 181, 182, 188, 191, 196, 199, 200, 300, 310, 311, 313, 316

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 20 2010

Keywords

• nonn
• base

Crossrefs

Cf. A100959.

Programs

Maple

A100959 := proc(n) option remember ; if n <= 3 then n ; else for a from procname(n-1)+1 do if numtheory[bigomega](a) <> 2 then return a; end if; end do: end if: end proc: read("transforms") ; for n from 1 to 300 do c := A100959(n) ; if isprime(digrev(c)) then printf("%d,",c) ; end if; end do: # R. J. Mathar, Apr 27 2010

Mathematica

Select[Range[400],PrimeOmega[#]!=2&&PrimeQ[FromDigits[Reverse[ IntegerDigits[ #]]]]&] (* Harvey P. Dale, Jan 03 2015 *)

Extensions

Corrected (20, 30, 50, 70, 76, 92, 110, 128, etc. inserted) by R. J. Mathar, Apr 27 2010