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Mountain emirps.
2

%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