A346021 Primes that are the first in a run of exactly 1 emirp.
97, 107, 113, 149, 157, 167, 179, 199, 311, 359, 389, 907, 1009, 1061, 1069, 1091, 1181, 1301, 1321, 1429, 1439, 1453, 1471, 1487, 1559, 1619, 1657, 1669, 1753, 1789, 1811, 1867, 1879, 1901, 1913, 1979, 3049, 3067, 3121, 3163, 3169, 3221, 3251, 3257, 3319
Offset: 1
Examples
a(1) = 97 because of the three consecutive primes 89, 97, 101 only 97 is an emirp and this is the first such occurrence.
Crossrefs
Programs
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Mathematica
emirpQ[p_] := (r = IntegerReverse[p]) != p && PrimeQ[r]; p = Select[Range[3400], PrimeQ]; p[[1 + Position[Partition[emirpQ /@ p, 3, 1], {False, True, False}] // Flatten]] (* Amiram Eldar, Jul 14 2021 *) -
Python
from sympy import isprime, nextprime def isemirp(p): s = str(p); return s != s[::-1] and isprime(int(s[::-1])) def aupto(limit): alst, pvec, evec, p = [], [2, 3, 5], [0, 0, 0], 7 while pvec[1] <= limit: if evec == [0, 1, 0]: alst.append(pvec[1]) pvec = pvec[1:] + [p]; evec = evec[1:] + [isemirp(p)]; p = nextprime(p) return alst print(aupto(3319)) # Michael S. Branicky, Jul 14 2021
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