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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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers k such that A062028(k) is in A246547.
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
Cf. A062028, A246547. Contains A242368.
Sequence in context: A164312 A068806 A090804 * A080281 A172446 A320331
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Mar 21 2021
STATUS
approved

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Last modified June 14 16:29 EDT 2024. Contains 373401 sequences. (Running on oeis4.)