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 A368238 #10 Dec 30 2023 23:15:22 %S A368238 91,14,34,74,35,95,38,301,901,721,731,361,371,391,791,922,142,362,382, %T A368238 703,713,133,943,763,973,793,914,134,334,934,974,194,305,905,145,745, %U A368238 755,365,965,785,395,995,106,706,146,346,746,166,386,917,377,118,358,758,958,778,119,749,779,799,3101 %N A368238 Semiprimes whose reversal is a prime, ordered by the prime. %H A368238 Robert Israel, <a href="/A368238/b368238.txt">Table of n, a(n) for n = 1..10000</a> %F A368238 a(n) = A004086(A085778(n)). %e A368238 a(4) = 74 because A115670(4) = 47 is the 4th prime whose reversal is a semiprime, and 74 is that reversal. %p A368238 rev:= proc(n) local L,i; %p A368238 L:= convert(n,base,10); %p A368238 add(L[-i]*10^(i-1),i=1..nops(L)) %p A368238 end proc: %p A368238 map(rev, select(p -> isprime(p) and numtheory:-bigomega(rev(p)) = 2, [seq(i,i=3..1000,2)]); %t A368238 s = {}; Do[If[2 == PrimeOmega[sm = FromDigits[Reverse[IntegerDigits[Prime[k]]]]], AppendTo[s, sm]], {k, 200}]; s %Y A368238 Cf. A001358, A004086, A085778, A115670. %K A368238 nonn,base %O A368238 1,1 %A A368238 _Zak Seidov_ and _Robert Israel_, Dec 18 2023