%I #19 Jul 14 2021 01:55:58
%S 1863,1979883,126639495,162037386,1979999883,1061283473946
%N Numbers k such that phi(k) = reversal(sigma(k)) - sigma(k).
%C If p = (22*10^m - 13)/9 is prime, then 3^4*p is a term of the sequence. This happens for m = 1, 4, 7, 12, 30, 94, 178, 196, 564, ... .
%C a(7) > 3*10^12.
%C If k is in the sequence A102953 then p = (22*10^k - 13)/9 is prime. 9 divides all known terms; is it true for all terms of this sequence? - _Farideh Firoozbakht_, Feb 06 2014
%e k = 1979999883 = 3^4*24444443 is a term, since sigma(k) = 2957777724 and 4277777592 - 2957777724 = 1319999868 = phi(k).
%Y Cf. A102953, A230012.
%K nonn,base,more
%O 1,1
%A _Giovanni Resta_, Feb 05 2014