A118732 - OEIS

%I #12 Dec 30 2021 13:35:24

%S 0,1,2,3,4,5,9,10,11,13,14,16,17,18,20,21,22,25,26,27,30,31,32,34,35,

%T 36,39,41,45,48,51,52,53,59,60,61,62,63,65,66,68,69,73,74,76,78,79,80,

%U 81,86,87,89,91,92,98,99,100,101,103,105,108,113,114,115,117,118,119,121

%N Numbers n such that 3^n has odd digit sum.

%C Numbers n such that A000244(n) is in A054684. - _Robert Israel_, Jun 28 2017

%H Robert Israel, <a href="/A118732/b118732.txt">Table of n, a(n) for n = 1..10000</a>

%p select(t -> convert(convert(3^t,base,10),`+`)::odd, [$0..1000]); # _Robert Israel_, Jun 28 2017

%t Select[Range[0, 121], Mod[ Plus @@ IntegerDigits[3^# ], 2] == 1 &] (* _Ray Chandler_, Jun 10 2006 *)

%t Select[Range[0,200],OddQ[Total[IntegerDigits[3^#]]]&] (* _Harvey P. Dale_, Dec 30 2021 *)

%o (PARI) isok(n) = (sumdigits(3^n) % 2) == 1; \\ _Michel Marcus_, Jun 28 2017

%Y Cf. A000244, A054684, A118731, A118735.

%K base,nonn

%O 1,3

%A _Zak Seidov_, May 22 2006