A137169 a(0) = 2; for n>0, a(n) = smallest number m > a(n-1) such that both m-n and m+n are primes.

2, 4, 5, 8, 9, 12, 13, 24, 39, 50, 51, 72, 85, 96, 117, 122, 123, 156, 175, 192, 213, 218, 219, 234, 247, 252, 255, 256, 279, 360, 367, 378, 399, 400, 423, 432, 455, 486, 525, 530, 531, 612, 619, 630, 657, 664, 687, 774, 775, 810, 837, 860, 915, 930, 937, 942

Offset: 0

Author

Vladimir Joseph Stephan Orlovsky, Apr 03 2008

Keywords

• nonn
• easy

Comments

A variant of A087711. - R. J. Mathar, Apr 09 2008

Examples

			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;
		

Crossrefs

See A087711 for another version.

Programs

Maple

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

Mathematica

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

Extensions

More terms from R. J. Mathar, Apr 09 2008

Typo in Mathematica code corrected by Vincenzo Librandi, Jun 15 2013