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 A156761 #15 May 27 2025 18:19:40
%S A156761 3,5,17,31,1201,128199521
%N A156761 Tribonacci primes that are also primes when their digits are reversed.
%C A156761 This is to A115347 as Fibonacci numbers A000045 are to A000213 tribonacci numbers. Except for palidromatic tribonacci numbers {3, 5, ...} these are tribonacci emirps, A000213 INTERSECTION A006567.
%C A156761 a(7), if it exists, is greater than A000213(10000). - _Dmitry Kamenetsky_, Mar 03 2009
%C A156761 a(7), if it exists, is greater than A000213(116404), testing tribonacci primes using A157611. - _Michael S. Branicky_, May 27 2025
%F A156761 {p such that p is in A000040 and p is in A000213 and R(p) = A004086(p) is in A000040} = {p such that p is in A056816 and R(p) = is in A000040}.
%e A156761 a(5) = 1201 because 1201 is prime, and is the 13th tribonacci number A000213(13), and R(1201) = A004086(1201) = 1021 is also prime. a(6) = 128199521 = the 10th tribonacci prime A056816(10), and its digital reverse 125991821 is also prime.
%t A156761 Select[LinearRecurrence[{1,1,1},{1,1,1},200],AllTrue[{#,IntegerReverse[ #]},PrimeQ]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 31 2019 *)
%Y A156761 Cf. A000040, A000045, A000213, A004086, A006567, A056816, A115347, A157611.
%K A156761 more,nonn,base
%O A156761 1,1
%A A156761 _Jonathan Vos Post_, Feb 15 2009