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Numbers of the form 6*k-+1 such that 6*k-1=prime and 6*k+1=nonprime.
2

%I #6 Nov 24 2016 06:05:15

%S 23,25,47,49,53,55,83,85,89,91,113,115,131,133,167,169,173,175,233,

%T 235,251,253,257,259,263,265,293,295,317,319,353,355,359,361,383,385,

%U 389,391,401,403,443,445,449,451,467,469,479,481,491,493,503,505,509,511

%N Numbers of the form 6*k-+1 such that 6*k-1=prime and 6*k+1=nonprime.

%t Select[Table[{6k-1, 6k+1}, {k, 1, 100}], PrimeQ[ #[[1]] ] && !PrimeQ[ #[[2]] ]&] // Flatten (* _Jean-François Alcover_, Nov 24 2016 *)

%Y A171688 U A171697 U A172015 U A172016 = A007310.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 22 2010

%E Entries checked by _R. J. Mathar_, Apr 14 2010