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A176597 Double primes: concatenation of the n-th prime with itself. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
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
Sequence in context: A257473 A116063 A131317 * A067087 A155709 A095044
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

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)