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A346027
Primes that are the first in a run of exactly 7 emirps.
3
11897, 18719, 125627, 743989, 910909, 920957, 928429, 941449, 1093571, 1407181, 1466533, 1518863, 1648553, 1770829, 3170743, 3300593, 7321943, 7682687, 7755581, 9013351, 12890047, 13267459, 14113199, 16413013, 16944341, 17316031, 18447001, 18490267, 18964111
OFFSET
1,1
COMMENTS
There are large gaps in this sequence because all terms need to begin with 1, 3, 7, or 9 otherwise the reversal is composite.
EXAMPLE
a(1) = 11897 because of the nine consecutive primes 11887, 11897, 11903, 11909, 11923, 11927, 11933, 11939, 11941 all except 11887 and 11941 are emirps and this is the first such occurrence.
MATHEMATICA
EmQ[n_]:=(s=IntegerReverse@n; PrimeQ@s&&n!=s);
Monitor[Do[p=Prime@k; If[MemberQ[{1, 3, 7, 9}, First@IntegerDigits@p], If[Boole[EmQ/@NextPrime[p, Range[-1, 7]]]=={0, 1, 1, 1, 1, 1, 1, 1, 0}, Print@p]], {k, 10^6}], p] (* Giorgos Kalogeropoulos, Jul 27 2021 *)
PROG
(Python) # uses code in A346026
print(aupto(10**7, runlength=7)) # Michael S. Branicky, Jul 14 2021
CROSSREFS
Subsequence of A006567 (emirps).
Sequence in context: A232673 A342351 A186603 * A222800 A230680 A218458
KEYWORD
nonn,base
AUTHOR
Lars Blomberg, Jul 14 2021
STATUS
approved