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%I #25 Sep 08 2022 08:44:59
%S 43,109,2221,2423,3433,4241,5857,7069,7877,8887,10099,102101,108107,
%T 112111,114113,124123,148147,154153,160159,172171,180179,192191,
%U 198197,202201,208207,210209,214213,238237,244243,262261,264263,268267,270269,282281,294293,300299
%N Primes formed by concatenating k with k-1.
%H Paul Tek, <a href="/A052089/b052089.txt">Table of n, a(n) for n = 1..10000</a>
%e 2423 is a prime and a concatenation of 24 and 23.
%t Sort[Select[FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[ Range[ 300,1,-1],2,1],PrimeQ]] (* _Harvey P. Dale_, May 09 2012 *)
%o (PARI) for(n=4,1e4,if(isprime(t=eval(Str(n,n-1))),print1(t", "))) \\ _Charles R Greathouse IV_, May 07 2013
%o (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
%o (Python)
%o from sympy import isprime
%o from itertools import count, islice
%o def agen(): yield from filter(isprime, (int(str(k)+str(k-1)) for k in count(2, 2)))
%o print(list(islice(agen(), 36))) # _Michael S. Branicky_, Aug 05 2022
%Y Cf. A030458, A052087, A052088.
%K nonn,base
%O 1,1
%A _Patrick De Geest_, Jan 15 2000
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