This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A052089 #27 Aug 20 2025 17:44:34
%S A052089 43,109,2221,2423,3433,4241,5857,7069,7877,8887,10099,102101,108107,
%T A052089 112111,114113,124123,148147,154153,160159,172171,180179,192191,
%U A052089 198197,202201,208207,210209,214213,238237,244243,262261,264263,268267,270269,282281,294293,300299
%N A052089 Primes formed by concatenating k with k-1.
%H A052089 Paul Tek, <a href="/A052089/b052089.txt">Table of n, a(n) for n = 1..10000</a>
%e A052089 2423 is a prime and a concatenation of 24 and 23.
%t A052089 Sort[Select[FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[ Range[ 300,1,-1],2,1],PrimeQ]] (* _Harvey P. Dale_, May 09 2012 *)
%t A052089 Select[Table[n 10^IntegerLength[n-1]+n-1,{n,2,300}],PrimeQ] (* _Harvey P. Dale_, Aug 20 2025 *)
%o A052089 (PARI) for(n=4,1e4,if(isprime(t=eval(Str(n,n-1))),print1(t", "))) \\ _Charles R Greathouse IV_, May 07 2013
%o A052089 (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 A052089 (Python)
%o A052089 from sympy import isprime
%o A052089 from itertools import count, islice
%o A052089 def agen(): yield from filter(isprime, (int(str(k)+str(k-1)) for k in count(2, 2)))
%o A052089 print(list(islice(agen(), 36))) # _Michael S. Branicky_, Aug 05 2022
%Y A052089 Cf. A030458, A052087, A052088.
%K A052089 nonn,base
%O A052089 1,1
%A A052089 _Patrick De Geest_, Jan 15 2000