A244085 Primes p such that the concatenation of p and 2*p-1 is also prime.

2, 5, 17, 29, 47, 61, 137, 149, 179, 181, 227, 251, 349, 367, 409, 457, 461, 479, 487, 557, 569, 617, 661, 691, 761, 787, 809, 821, 859, 911, 971, 977, 997, 1039, 1117, 1129, 1151, 1249, 1277, 1367, 1439, 1447, 1459, 1481, 1559, 1571, 1667, 1747, 1801, 1831

Offset

1,1

Comments

The corresponding prime numbers are: (23, 59, 1733, 2957, 4793, 61121, ...).

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

17 in this sequence because the concatenation of 17 and 33 is 1733 prime.

Mathematica

p2pQ[n_]:=PrimeQ[FromDigits[IntegerDigits/@Join[n, 2 n - 1]]]; Select[Prime[Range[900]], p2pQ]

Crossrefs

Cf. A168164.

Sequence in context: A195271 A077217 A120847 * A019353 A106882 A172122

Adjacent sequences: A244082 A244083 A244084 * A244086 A244087 A244088

Keyword

nonn,base

Author

Vincenzo Librandi, Jun 22 2014

Status

approved