A105266 a(1)=1 and, for n>1, a(n) is the smallest integer greater than a(n-1) such that no three terms x,y,z of the sequence, with x<y<z, satisfy z-y=y-x+1.

1, 2, 3, 7, 8, 9, 19, 20, 21, 25, 26, 27, 55, 56, 57, 61, 62, 63, 73, 74, 75, 79, 80, 81, 163, 164, 165, 169, 170, 171, 181, 182, 183, 187, 188, 189, 217, 218, 219, 223, 224, 225, 235, 236, 237, 241, 242, 243, 487, 488, 489, 493, 494, 495, 505, 506, 507, 511, 512

Offset

1,2

Comments

It appears that {a(n)} consists exactly of those positive integers whose base-3 representation satisfies (i) only 0's follow a 1 and (ii) a final run of 0's must follow a 1.

Links

Table of n, a(n) for n=1..59.

Crossrefs

Cf. A003278.

Sequence in context: A246440 A332699 A347153 * A246448 A054996 A338691

Adjacent sequences: A105263 A105264 A105265 * A105267 A105268 A105269

Keyword

nonn

Author

John W. Layman, Apr 15 2005

Status

approved