A118733 Numbers k such that 3^k has even digit sum.

6, 7, 8, 12, 15, 19, 23, 24, 28, 29, 33, 37, 38, 40, 42, 43, 44, 46, 47, 49, 50, 54, 55, 56, 57, 58, 64, 67, 70, 71, 72, 75, 77, 82, 83, 84, 85, 88, 90, 93, 94, 95, 96, 97, 102, 104, 106, 107, 109, 110, 111, 112, 116, 120, 122, 125, 126, 129, 132, 135, 136, 138, 139

Offset: 1

Author

Zak Seidov, May 22 2006

Keywords

• nonn
• base

Links

• Clinton Walker, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004166, A118730, A118734.

Programs

Mathematica

Select[Range[140], Mod[ Plus @@ IntegerDigits[3^# ], 2] == 0 &] (* Ray Chandler, Jun 10 2006 *)
Select[Range[150],EvenQ[Total[IntegerDigits[3^#]]]&] (* Harvey P. Dale, Mar 12 2013 *)

Python

from gmpy2 import digits
def ok(n): return sum(map(int, digits(3**n)))&1 == 0
print([k for k in range(140) if ok(k)]) # Michael S. Branicky, May 11 2025