A043687 a(n) = (s(n)-1)/2, where s(n) is the n-th number whose base-2 representation has exactly 3 runs.

2, 4, 5, 6, 8, 9, 11, 12, 13, 14, 16, 17, 19, 23, 24, 25, 27, 28, 29, 30, 32, 33, 35, 39, 47, 48, 49, 51, 55, 56, 57, 59, 60, 61, 62, 64, 65, 67, 71, 79, 95, 96, 97, 99, 103, 111, 112, 113, 115, 119, 120, 121, 123, 124, 125, 126, 128, 129

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Comments

a(n) = A238246(n) - 1. - Reinhard Zumkeller, Feb 20 2014

Links

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

Crossrefs

Cf. A238246.

Programs

Mathematica

(# - 1)/2&/@Select[Range[1000], Length[Split[IntegerDigits[#, 2]]]==3&] (* Vincenzo Librandi, Feb 22 2014 *)