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 A182721 #15 Dec 31 2021 06:05:46 %S A182721 1231,1321,1381,1471,1741,1831,12491,12641,12841,13591,13751,13781, %T A182721 13841,14591,14621,14821,14831,14891,15731,15791,18731,19421,19531, %U A182721 19541,19751,19841,123731,123821,124951,124981,125641,125651,125791,125821,125941,126761,126851 %N A182721 Mountain emirps. %C A182721 Intersection of emirps A006567 and mountain numbers A134941. %C A182721 The smallest mountain emirp 1231 and other terms of this sequence was mentioned by Loungrides in Prime Curios! (see link). %C A182721 Question: How many are there? %C A182721 There are 602 such terms. - _Michael S. Branicky_, Dec 31 2021 %H A182721 Michael S. Branicky, <a href="/A182721/b182721.txt">Table of n, a(n) for n = 1..602</a> (full sequence) %H A182721 G. L. Honaker, Jr. and C. K. Caldwell, <a href="https://primes.utm.edu/curios/page.php?number_id=2161">Prime Curios! 1231</a> %F A182721 A006567 INTERSECT A134941. %e A182721 Illustration of a(11) = 13751 as a mountain emirp: %e A182721 . . . . . %e A182721 . . . . . %e A182721 . . 7 . . %e A182721 . . . . . %e A182721 . . . 5 . %e A182721 . . . . . %e A182721 . 3 . . . %e A182721 . . . . . %e A182721 1 . . . 1 %o A182721 (Python) # uses A134941() %o A182721 from sympy import isprime %o A182721 def is_emirp(n): %o A182721 if not isprime(n): return False %o A182721 revn = int(str(n)[::-1]) %o A182721 return n != revn and isprime(revn) %o A182721 print([k for k in A134941() if is_emirp(k)]) # _Michael S. Branicky_, Dec 31 2021 %Y A182721 Cf. A006567, A134941, A134951, A135417, A173071. %K A182721 nonn,base,fini,full %O A182721 1,1 %A A182721 _Omar E. Pol_, Dec 21 2010 %E A182721 More terms from _Nathaniel Johnston_, Dec 29 2010 %E A182721 Terms a(31) and beyond from _Michael S. Branicky_, Dec 31 2021