A031951 Numbers with exactly two distinct base-6 digits.

6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 36, 37, 42, 44, 45, 46, 47, 49, 50, 55, 57, 61, 64, 67, 71, 72, 74, 79, 80, 84, 85, 87, 88, 89, 92, 93, 98, 100, 104, 107, 108, 111, 115, 117

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• easy

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Index entries for 6-automatic sequences.

Crossrefs

Cf. A007092, A031948, A031949, A031950, A031952, A031953, A031954, A031955.

Programs

Maple

M:= 6: # get all terms < 6^M
sort([seq(seq(seq(seq(add(6^(m-j)*`if`(member(j,S2),d2,d1),j=1..m)  ,
S2 = combinat:-powerset({$2..m}) minus {{}}),
d2 = {$0..5} minus {d1}), d1 = 1..5), m=2..M)]);# Robert Israel, Dec 03 2015

Mathematica

fQ[n_] := Length@ Union@ IntegerDigits[n, 6] == 2; Select[Range@117, fQ] (* Robert G. Wilson v, Dec 03 2015 *)