A101594 Numbers with exactly two distinct decimal digits, neither of which is 0.

12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24, 25, 26, 27, 28, 29, 31, 32, 34, 35, 36, 37, 38, 39, 41, 42, 43, 45, 46, 47, 48, 49, 51, 52, 53, 54, 56, 57, 58, 59, 61, 62, 63, 64, 65, 67, 68, 69, 71, 72, 73, 74, 75, 76, 78, 79, 81, 82, 83, 84, 85, 86, 87, 89, 91, 92, 93, 94, 95, 96, 97, 98, 112, 113, 114, 115, 116, 117, 118, 119, 121, 122, 131

Offset: 1

Author

David Wasserman, Dec 07 2004

Keywords

• base
• easy
• nonn
• less
• look

Comments

First differs from A125290 at a(83) = 131 != 123 = A101594(83). - Michael S. Branicky, Dec 13 2021

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Index entries for 10-automatic sequences.

Crossrefs

Cf. A083985, A031955, A004719, A043537, A168046.

Subsequence of A052382, A125290.

Programs

Haskell

a101594 n = a101594_list !! (n-1)
a101594_list = filter ((== 2) . a043537) a052382_list
-- Reinhard Zumkeller, Jun 18 2013

Mathematica

Select[Range[200], FreeQ[#, 0] && Length[Union[#]] == 2 & [IntegerDigits[#]] &] (* Paolo Xausa, May 06 2024 *)

Python

def ok(n): s = set(str(n)); return len(s) == 2 and "0" not in s
print([k for k in range(132) if ok(k)]) # Michael S. Branicky, Dec 13 2021

Formula

A168046(a(n)) * A043537(A004719(a(n))) = 2. - Reinhard Zumkeller, Jun 18 2013