A345389 - OEIS

%I #12 Jun 18 2021 12:24:19

%S 9049,9631,125329,148249,180289,1000651,1027591,1250023,1460479,

%T 1674931,1825891,1889221,3989683,9003703,9041143,9049231,10612219,

%U 14499601,14663479,16333459,18005983,18428101,90876631,98087809,98873821,100720513,100922011,101274443,108344311,121623511,123736969

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

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

%p revdigs:= proc(n) local L,i; L:= convert(n,base,10); add(L[-i]*10^(i-1),i=1..nops(L)) end proc:

%p isemirp:= proc(n) local r; if not isprime(n) then return false fi;

%p r:= revdigs(n); r <> n and isprime(r) end proc:

%p E:= select(isemirp, [seq(i,i=11..10^5,2)]):

%p EP:= map(proc(x) local i; seq(x^i,i=2..floor(log[x](10^10))) end proc,E):

%p EPR:= map(revdigs,EP):

%p sort(select(isprime,EPR));

%Y Cf. A006567, A143260.

%K nonn,base,look

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Jun 17 2021