A345389 Primes that are not emirps but whose digit reversal is a power of an emirp.

9049, 9631, 125329, 148249, 180289, 1000651, 1027591, 1250023, 1460479, 1674931, 1825891, 1889221, 3989683, 9003703, 9041143, 9049231, 10612219, 14499601, 14663479, 16333459, 18005983, 18428101, 90876631, 98087809, 98873821, 100720513, 100922011, 101274443, 108344311, 121623511, 123736969

Offset

1,1

Links

Table of n, a(n) for n=1..31.

Example

a(3) = 125329 is a term because it is prime and its reversal 923521 = 31^4 where 31 is an emirp.

Maple

revdigs:= proc(n) local L, i; L:= convert(n, base, 10); add(L[-i]*10^(i-1), i=1..nops(L)) end proc:
isemirp:= proc(n) local r; if not isprime(n) then return false fi;
r:= revdigs(n); r <> n and isprime(r) end proc:
E:= select(isemirp, [seq(i, i=11..10^5, 2)]):
EP:= map(proc(x) local i; seq(x^i, i=2..floor(log[x](10^10))) end proc, E):
EPR:= map(revdigs, EP):
sort(select(isprime, EPR));

Crossrefs

Cf. A006567, A143260.

Sequence in context: A210179 A161610 A204535 * A202914 A252443 A061135

Adjacent sequences: A345386 A345387 A345388 * A345390 A345391 A345392

Keyword

nonn,base,look

Author

J. M. Bergot and Robert Israel, Jun 17 2021

Status

approved