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%I #23 Nov 25 2022 07:21:37
%S 0,1,2,3,4,5,9,10,11,13,16,17,21,27,31,35,36,39,114,119,973,1005,1010,
%T 1025,3006,3029,3040,9128,9215,9227,9316,27431,27442,27515,27519,
%U 27554,82632,82746,82763,82784,83111,246838,247206,247388,247406,247447,741310,742154
%N Numbers k such that digit sum of 3^k is a power of 3.
%C a(47) > 677750. - _Ray Chandler_, Jun 16 2006
%C a(47) <= 741310. If a(47) < 741310 then a(47) < 720000. a(48) <= 742154. If a(48) < 741310 then a(48) < 720000. - _David A. Corneth_, Nov 23 2022
%F A067500(n) = 3^a(n).
%e 3^39 = 4052555153018976267 with digit sum 81 = 3^4, so 39 is a term.
%t Do[If[IntegerQ[Log[3, Plus @@ IntegerDigits[3^n]]], Print[n]], {n, 0, 677750}];
%o (PARI) is(n) = my(s = sumdigits(3^n)); s == 3^logint(s, 3) \\ _David A. Corneth_, Nov 23 2022
%Y Cf. A004166 (sum of digits of 3^n).
%K base,nonn
%O 1,3
%A _Zak Seidov_, May 24 2006
%E Extended by _Ray Chandler_, Jun 16 2006
%E a(47) and a(48) from _Jon E. Schoenfield_, Nov 25 2022
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