A078626 Primes p which concatenated with p+2 give a prime.

7, 37, 61, 109, 151, 181, 211, 271, 277, 331, 337, 367, 421, 439, 457, 487, 541, 619, 661, 691, 727, 751, 829, 859, 877, 907, 1039, 1087, 1129, 1201, 1237, 1279, 1321, 1399, 1489, 1549, 1609, 1621, 1699, 1741, 1777, 1831, 1999, 2341, 2347, 2767, 2851

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

37 is a prime which, concatenated with 37+2=39, gives 3739, a prime; so 37 belongs to the sequence.

Mathematica

a = {}; For[i = 1, i <= 10^3, i++, p = Prime[i]; If[PrimeQ[ToExpression[ToString[p] <> ToString[p + 2]]], a = Append[a, p]]]; a
conQ[n_]:=PrimeQ[FromDigits[Join[IntegerDigits[n], IntegerDigits[n+2]]]]; Select[Prime[Range[500]], conQ] (* Harvey P. Dale, May 28 2014 *)

Crossrefs

Sequence in context: A217561 A003521 A155943 * A093389 A093342 A336494

Adjacent sequences: A078623 A078624 A078625 * A078627 A078628 A078629

Keyword

base,easy,nonn

Author

Joseph L. Pe, Dec 11 2002

Status

approved