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 A068998 #22 Mar 27 2024 12:30:26
%S A068998 2,3,4,5,6,7,8,9,11,12,13,16,17,18,19,21,22,23,24,25,27,29,31,32,33,
%T A068998 36,37,39,41,43,44,46,47,48,49,51,53,54,58,59,61,63,64,66,67,70,71,72,
%U A068998 73,79,81,82,83,88,89,92,93,96,97,99,101,103,107,108,109,111
%N A068998 Numbers m such that the concatenation of the prime factors of m (in increasing order and ignoring multiplicity) is prime.
%H A068998 Michael S. Branicky, <a href="/A068998/b068998.txt">Table of n, a(n) for n = 1..10000</a>
%e A068998 The prime factors of 51 are 3 and 17 and their concatenation 317 is prime, so 51 belongs to the sequence.
%p A068998 q:= n-> isprime(parse(cat(sort(map(i-> i[1], ifactors(n)[2]))[]))):
%p A068998 select(q, [$2..222])[]; # _Alois P. Heinz_, Mar 27 2024
%t A068998 Reap[Do[If[PrimeQ[#], Sow[n]] &[FromDigits[Join @@ Map[IntegerDigits, FactorInteger[n][[All, 1]] ] ] ], {n, 120}]][[-1, 1]] (* _Michael De Vlieger_, Mar 27 2024 *)
%o A068998 (Python)
%o A068998 def a(n):
%o A068998 b, s = bin(n)[2:], str(n)
%o A068998 return int("".join(d for i, d in enumerate(s) if b[i]=="1"))
%o A068998 print([a(n) for n in range(1, 81)]) # _Michael S. Branicky_, Mar 27 2024
%Y A068998 Cf. A000040, A027748, A246655, A343027.
%K A068998 base,easy,nonn
%O A068998 1,1
%A A068998 _Joseph L. Pe_, Mar 16 2002
%E A068998 Missing 4 inserted and more terms from _Sean A. Irvine_, Mar 27 2024