A074276 Positions of occurrences of 2,1,1,2,1 in the Kolakoski sequence A000002.

3, 12, 21, 27, 30, 39, 47, 57, 66, 69, 84, 93, 102, 111, 114, 120, 129, 139, 156, 166, 174, 183, 189, 192, 207, 216, 219, 225, 237, 243, 252, 264, 270, 273, 282, 290, 309, 318, 327, 336, 351, 354, 363, 380, 386, 398, 407, 416, 425, 437, 443, 462, 471, 480

Offset

1,1

Links

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Example

The Kolakoski sequence begins 1,2,2,1,1,2,1,2,2,1,2,2,1,1,2,1,..., so 2,1,1,2,1 occurs at positions 3 and 12.

Mathematica

a2 = {1, 2, 2}; Do[a2 = Join[a2, {1 + Mod[n - 1, 2]}], {n, 3, 400}, {i, 1, a2[[n]]}]; a2 //. {a___, 2, 1, 1, 2, 1, b___} :> {a, 0, 1, 1, 2, 1, b} // Flatten // Position[#, 0] & // Flatten (* Jean-François Alcover, Jun 18 2013 *)

Crossrefs

Cf. A074275, A074277.

Sequence in context: A256131 A080767 A043465 * A055041 A061819 A017197

Adjacent sequences: A074273 A074274 A074275 * A074277 A074278 A074279

Keyword

nonn,easy

Author

Jon Perry, Sep 21 2002

Extensions

Extended and offset corrected by Nathaniel Johnston, May 02 2011

Status

approved