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