A116601 a(0) = a(1) = 0; for n >= 2, a(n) = floor(sqrt(2^(n-2)-1)).

0, 0, 0, 1, 1, 2, 3, 5, 7, 11, 15, 22, 31, 45, 63, 90, 127, 181, 255, 362, 511, 724, 1023, 1448, 2047, 2896, 4095, 5792, 8191, 11585, 16383, 23170, 32767, 46340, 65535, 92681, 131071, 185363, 262143, 370727, 524287, 741455, 1048575, 1482910, 2097151, 2965820, 4194303, 5931641

Offset: 0

Author

Roger L. Bagula, Mar 28 2006

Keywords

• nonn

Comments

Numbers k such that k^2 is the largest square less than the next power of 2. - Hugo Pfoertner, Sep 30 2022

Links

• G. C. Greubel, Table of n, a(n) for n = 0..440

Crossrefs

Cf. A002193, A357754.

Programs

Mathematica

Join[{0, 0}, Table[Floor[Sqrt[2^(n - 2) - 1]], {n, 2, 50}]] (* G. C. Greubel, Oct 28 2017 *)

Python

from math import isqrt
def A116601(n): return isqrt((1< 1 else 0 # Chai Wah Wu, Oct 13 2022

Extensions

Edited by N. J. A. Sloane, May 10 2007