A249721 Numbers whose base-3 representation consists entirely of 0's and 2's, except possibly for a single pair of adjacent 1's among them.

0, 2, 4, 6, 8, 12, 14, 18, 20, 22, 24, 26, 36, 38, 42, 44, 54, 56, 58, 60, 62, 66, 68, 72, 74, 76, 78, 80, 108, 110, 114, 116, 126, 128, 132, 134, 162, 164, 166, 168, 170, 174, 176, 180, 182, 184, 186, 188, 198, 200, 204, 206, 216, 218, 220, 222, 224, 228, 230, 234, 236, 238, 240, 242, 324

Offset: 0

Author

Antti Karttunen, Nov 14 2014

Keywords

• nonn
• base

Comments

9 divides neither C(s-1,s/2) (= A001700(s/2)) nor C(s,s/2) (= A000984(s/2)) if and only if s = a(n).

Examples

			   2, which in base 3 is also '2', satisfies the condition, thus it is included;
   4, which in base 3 is  '11', is included;
   6, which in base 3 is  '20', is included;
   8, which in base 3 is  '22', is included;
  12, which in base 3 is '110', is included;
  14, which in base 3 is '112', is included;
however, e.g., 13, 40, and 130, whose ternary representations are '111', '1111' and '11211' respectively, are not included, because they all contain more than one pair of 1's.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 0..8192

Crossrefs

Cf. A007089, A051382, A249719, A249720, A001700, A000984, A117966, A249733.

Formula

a(n) = 2 * A051382(n).