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Numbers n such that the smallest exponent k for n and n^k to have common digits is 4.
2

%I #11 Jul 16 2019 17:21:50

%S 22,47,92,157,187,188,192,552,558,577,707,772,922,2522,8338,17177,

%T 66888,575757,929522,1717177,8888588

%N Numbers n such that the smallest exponent k for n and n^k to have common digits is 4.

%e 22^2=484 and 22^3=10648 have no digits in common with 22, but 22^4=234256 has some, so 22 is in the sequence.

%o (PARI) a253600(n) = {sd = Set(vecsort(digits(n))); k=2; while (#setintersect(sd, Set(vecsort(digits(n^k)))) == 0, k++); k;}

%o isok(n) = a253600(n) == 4;

%Y Cf. A029790, A103173, A189056, A253600, A253601.

%K nonn,base,more

%O 1,1

%A _Michel Marcus_, Jan 05 2015