A293331 Greatest integer k such that k/2^n < sqrt(5).

2, 4, 8, 17, 35, 71, 143, 286, 572, 1144, 2289, 4579, 9158, 18317, 36635, 73271, 146542, 293085, 586171, 1172343, 2344687, 4689374, 9378748, 18757497, 37514995, 75029990, 150059981, 300119963, 600239927, 1200479854, 2400959708, 4801919417, 9603838834

Offset

0,1

Links

Clark Kimberling, Table of n, a(n) for n = 0..1000

Formula

a(n) = floor(r*2^n), where r = sqrt(5).

a(n) = A293332(n) - 1.

Mathematica

z = 120; r = Sqrt[5];
Table[Floor[r*2^n], {n, 0, z}];   (* A293331 *)
Table[Ceiling[r*2^n], {n, 0, z}]; (* A293332 *)
Table[Round[r*2^n], {n, 0, z}];   (* A293333 *)

Prog

(Python)
from math import isqrt
def A293331(n): return isqrt(5*(1<<(n<<1))) # Chai Wah Wu, Jul 28 2022

Crossrefs

Cf. A001633, A293332, A293333.

Sequence in context: A026392 A266897 A018094 * A309908 A001357 A309462

Adjacent sequences: A293328 A293329 A293330 * A293332 A293333 A293334

Keyword

nonn,easy

Author

Clark Kimberling, Oct 10 2017

Status

approved