

A342773


Numbers k such that k + sum of digits of k is a proper prime power.


1



2, 4, 8, 17, 18, 25, 38, 72, 118, 121, 161, 234, 245, 275, 329, 347, 521, 614, 720, 830, 944, 998, 1016, 1318, 1355, 1664, 1829, 2041, 2169, 2183, 2189, 2384, 2786, 3115, 3464, 3710, 4082, 4472, 4891, 4900, 5027, 5315, 6230, 6543, 6836, 7889, 8173, 10190, 10592, 10601, 11435, 11858, 12154, 12752
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OFFSET

1,1


COMMENTS

Proper prime powers in the sequence include 4, 8, 25, 121. Are there any others?


LINKS



EXAMPLE

a(4) = 17 is a term because 17+1+7 = 25 = 5^2.


MAPLE

filter:= proc(n) local s, F;
s:= n + convert(convert(n, base, 10), `+`);
F:= ifactors(s)[2];
nops(F)=1 and F[1][2]>1
end proc:
select(filter, [$1..20000]);


PROG

(PARI) isok(k) = isprimepower(k + sumdigits(k)) > 1; \\ Michel Marcus, Mar 22 2021


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



