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A052089 Primes formed by concatenating n with n-1. 27
43, 109, 2221, 2423, 3433, 4241, 5857, 7069, 7877, 8887, 10099, 102101, 108107, 112111, 114113, 124123, 148147, 154153, 160159, 172171, 180179, 192191, 198197, 202201, 208207, 210209, 214213, 238237, 244243, 262261, 264263, 268267, 270269 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paul Tek, Table of n, a(n) for n = 1..10000

EXAMPLE

2423 is a prime and a concatenation of 24 and 23.

MATHEMATICA

Sort[Select[FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[ Range[ 300, 1, -1], 2, 1], PrimeQ]] (* Harvey P. Dale, May 09 2012 *)

PROG

(PARI) for(n=4, 1e4, if(isprime(t=eval(Str(n, n-1))), print1(t", "))) \\ Charles R Greathouse IV, May 07 2013

(MAGMA) [Seqint(Intseq(n-1) cat Intseq(n)): n in [2..300 by 2] | IsPrime(Seqint(Intseq(n-1) cat Intseq(n)))]; // Marius A. Burtea, Mar 21 2019

CROSSREFS

Cf. A030458, A052087, A052088.

Sequence in context: A142055 A052088 A068699 * A260809 A039471 A104783

Adjacent sequences:  A052086 A052087 A052088 * A052090 A052091 A052092

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jan 15 2000

STATUS

approved

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Last modified August 10 22:22 EDT 2020. Contains 336403 sequences. (Running on oeis4.)