A342773 Numbers k such that k + sum of digits of k is a proper prime power.

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

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

Robert Israel, Table of n, a(n) for n = 1..1001

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

Adjacent sequences: A342770 A342771 A342772 * A342774 A342775 A342776

Keyword

nonn,base

Author

J. M. Bergot and Robert Israel, Mar 21 2021

Status

approved