A176597 Double primes: concatenation of the n-th prime with itself.

22, 33, 55, 77, 1111, 1313, 1717, 1919, 2323, 2929, 3131, 3737, 4141, 4343, 4747, 5353, 5959, 6161, 6767, 7171, 7373, 7979, 8383, 8989, 9797, 101101, 103103, 107107, 109109, 113113, 127127, 131131, 137137, 139139, 149149, 151151, 157157, 163163

Offset

1,1

Links

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

Example

Concatenation 2 and 2 is 22; 3 and 3 is 33; 5 and 5 is 55; etc.

Mathematica

dp[n_] := Module[{idn = IntegerDigits[n]}, FromDigits[Join[idn, idn]]]; dp /@ Prime[Range[40]] (* Harvey P. Dale, Jun 02 2011 *)

Prog

(Magma) [Seqint(Intseq(p) cat Intseq(p)): p in PrimesUpTo(200)]; // Vincenzo Librandi, Mar 14 2013
(PARI) a(n) = { my(p=Str(prime(n))); eval(concat(p, p)); } /* Joerg Arndt, Mar 14 2013 */

Crossrefs

Cf. A000040, A020338, A067087.

Sequence in context: A257473 A116063 A131317 * A067087 A155709 A095044

Adjacent sequences: A176594 A176595 A176596 * A176598 A176599 A176600

Keyword

nonn,base

Author

Vincenzo Librandi, Apr 21 2010

Extensions

Edited by Charles R Greathouse IV and R. J. Mathar, Apr 23 2010

Status

approved