A043689 a(n) = (s(n)-1)/2, where s(n) is the n-th number whose base-2 representation has exactly 7 runs.

42, 74, 82, 84, 85, 86, 90, 106, 138, 146, 148, 149, 150, 154, 162, 164, 165, 166, 168, 169, 171, 172, 173, 174, 178, 180, 181, 182, 186, 202, 210, 212, 213, 214, 218, 234, 266, 274, 276, 277, 278, 282, 290, 292, 293, 294, 296

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Comments

a(n) = A238248(n) - 1. - Reinhard Zumkeller, Feb 20 2014

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A238248.

Programs

Mathematica

(# - 1)/2&/@Select[Range[50], Length[Split[IntegerDigits[#, 2]]]==7&] (* Vincenzo Librandi, Feb 22 2014 *)