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

1,2

Comments

Numbers such that A099551(n) = 1.

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

Links

Table of n, a(n) for n=1..57.

Formula

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

Example

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.

Prog

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

Crossrefs

Cf. A099551.

Sequence in context: A320448 A115797 A336627 * A003596 A018600 A018408

Adjacent sequences: A242310 A242311 A242312 * A242314 A242315 A242316

Keyword

nonn,base,easy

Author

J. Lowell, May 10 2014

Extensions

More terms from Michel Marcus, May 14 2014

Status

approved