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 A367793 #14 Jun 21 2025 01:56:34 %S A367793 2,3,5,7,11,23,29,41,43,47,61,67,83,89,101,131,151,181,191,211,223, %T A367793 227,233,251,293,313,353,373,383,401,409,419,421,431,433,449,457,487, %U A367793 491,571,599,601,607,617,619,631,643,647,727,757,787,797,809,821,827,829,853,859,877,883,919,929,2011 %N A367793 Primes p such that the sum of p and its reversal is a semiprime. %C A367793 Terms > 11 with an even number of digits have an even first digit. %H A367793 Robert Israel, <a href="/A367793/b367793.txt">Table of n, a(n) for n = 1..10000</a> %e A367793 a(6) = 23 is a term because 23 is a prime and 23 + 32 = 55 = 5 * 11 is a semiprime. %p A367793 digrev:= proc(n) local L,i; %p A367793 L:= convert(n,base,10); %p A367793 add(L[-i]*10^(i-1),i=1..nops(L)) %p A367793 end proc: %p A367793 select(p -> isprime(p) and numtheory:-bigomega(p+digrev(p))=2, [2,seq(i,i=3..10000,2)]); %t A367793 Select[Prime[Range[10^3]], 2 == PrimeOmega[# + FromDigits[Reverse[IntegerDigits[#]]]] &] %Y A367793 Cf. A001358, A056964, A061783. %K A367793 nonn,base %O A367793 1,1 %A A367793 _Zak Seidov_ and _Robert Israel_, Nov 30 2023