A173664 Sums of 2 primes that are not product of 2 primes.

5, 7, 8, 12, 13, 16, 18, 19, 20, 24, 28, 30, 31, 32, 36, 40, 42, 43, 44, 45, 48, 50, 52, 54, 56, 60, 61, 63, 64, 66, 68, 70, 72, 73, 75, 76, 78, 80, 81, 84, 88, 90, 92, 96, 98, 99, 100, 102, 103, 104, 105, 108, 109, 110, 112, 114, 116, 120, 124, 126

Offset

1,1

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Formula

A014091 \ A001358. - R. J. Mathar, Nov 24 2010

Maple

a:= proc(n) option remember; local k;
      if n=1 then 5
      else for k from a(n-1)+1 do
             if add (i[2], i=ifactors(k)[2])=2 then next fi;
             if irem (k, 2)=0 or isprime (k-2) then break fi
           od; k
      fi
    end:
seq (a(n), n=1..60);  # Alois P. Heinz, Nov 24 2010

Mathematica

Select[Union[Flatten[Table[Prime[i] + Prime[j], {i, 25}, {j, 25}]]], PrimeOmega[#] != 2 &] (* Alonso del Arte, Feb 08 2013 *)

Prog

(PARI) is(n)=if(n%2, isprime(n-2)&&bigomega(n)!=2, n>2&&!isprime(n/2)) \\ above 4 * 10^18, conditional on the Goldbach conjecture Charles R Greathouse IV, Feb 09 2013

Crossrefs

Cf. A157931, A089268.

Sequence in context: A327960 A347127 A061813 * A171420 A047384 A257772

Adjacent sequences: A173661 A173662 A173663 * A173665 A173666 A173667

Keyword

nonn

Author

Juri-Stepan Gerasimov, Nov 24 2010

Extensions

More terms from Alois P. Heinz, Nov 24 2010

Status

approved