A074039 If (n, n+2) is the k-th twin prime pair then k else 0.

0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 1

Author

Reinhard Zumkeller, Aug 13 2002

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001359, A006512, A049084, A074038.

Programs

Mathematica

seq[max_] := Module[{t = Select[Range[max], And @@ PrimeQ[# + {0, 2}] &], v}, v = Table[0, {max}]; v[[t]] = Range[Length[t]]; v]; seq[100] (* Amiram Eldar, Apr 06 2025 *)

Formula

A001359(a(n)) = n, A006512(a(n)) = n+2.