A242313 Numbers belonging to a geometric sequence whose ratio is 2 and whose first term ends in 1.

1, 2, 4, 8, 11, 16, 21, 22, 31, 32, 41, 42, 44, 51, 61, 62, 64, 71, 81, 82, 84, 88, 91, 101, 102, 111, 121, 122, 124, 128, 131, 141, 142, 151, 161, 162, 164, 168, 171, 176, 181, 182, 191, 201, 202, 204, 211, 221, 222, 231, 241, 242, 244, 248, 251, 256, 261

Offset: 1

Author

J. Lowell, May 10 2014

Keywords

• nonn
• base
• easy

Comments

Numbers such that A099551(n) = 1.

Numbers of the form 2^m * (10n + 1). - Charles R Greathouse IV, May 14 2014

Examples

			176 is in the sequence because it belongs to 11, 22, 44, 88, 176, with first term 11.
96, which belongs to 3, 6, 12, 24, 48, 96 with first term 3, is not a term.
		

Crossrefs

Cf. A099551.

Programs

PARI

isok(n) = ((n/2^valuation(n, 2)) % 10) == 1; \\ Michel Marcus, May 14 2014

Formula

a(n) = 5n + O(log n). - Charles R Greathouse IV, May 14 2014

Extensions

More terms from Michel Marcus, May 14 2014