A137169 - OEIS

%I #9 Sep 21 2015 01:19:10

%S 2,4,5,8,9,12,13,24,39,50,51,72,85,96,117,122,123,156,175,192,213,218,

%T 219,234,247,252,255,256,279,360,367,378,399,400,423,432,455,486,525,

%U 530,531,612,619,630,657,664,687,774,775,810,837,860,915,930,937,942

%N a(0) = 2; for n>0, a(n) = smallest number m > a(n-1) such that both m-n and m+n are primes.

%C A variant of A087711. - _R. J. Mathar_, Apr 09 2008

%e 4-1=3 prime, 4+1=5 prime; 5-2=3, 5+2=7; 8-3=5, 8+3=11; 9-4=5, 9+4=13;

%p A137169 := proc(n) option remember ; if n = 0 then RETURN(2) ; fi ; for a from A137169(n-1)+1 do if isprime(a-n) and isprime(a+n) then RETURN(a) ; fi ; od: end: seq(A137169(n),n=0..80) ; # _R. J. Mathar_, Apr 09 2008

%t s = ""; k = 0; For[i = 2, i < 22^2, If[PrimeQ[i - k] && PrimeQ[i + k], s = s <> ToString[i] <> ","; k++ ]; i++ ]; Print[s]

%Y See A087711 for another version.

%K nonn,easy

%O 0,1

%A _Vladimir Joseph Stephan Orlovsky_, Apr 03 2008

%E More terms from _R. J. Mathar_, Apr 09 2008

%E Typo in Mathematica code corrected by _Vincenzo Librandi_, Jun 15 2013