A031953 Numbers with exactly two distinct base-8 digits.

8, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 72, 74, 75, 76, 77, 78, 79, 81, 82, 89, 91, 97, 100, 105

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• easy

Links

• Index entries for 2-automatic sequences.

Crossrefs

Cf. A031948 - A031955.

Programs

Mathematica

Select[Range[100],Length[Union[IntegerDigits[#,8]]]==2&] (* Harvey P. Dale, Feb 15 2019 *)

PARI

is(n)=#Set(digits(n, 8))==2 \\ Charles R Greathouse IV, Feb 15 2017

Python

def ok(n): return len(set(oct(n)[2:])) == 2
print(list(filter(ok, range(106)))) # Michael S. Branicky, Aug 10 2021

Extensions

Name edited by Michael S. Branicky, Aug 10 2021