A017958 Powers of sqrt(18) rounded down.

1, 4, 18, 76, 324, 1374, 5832, 24743, 104976, 445375, 1889568, 8016758, 34012224, 144301645, 612220032, 2597429617, 11019960576, 46753733110, 198359290368, 841567195983, 3570467226624, 15148209527700

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..800

Formula

a(n) = floor(sqrt(18^n)). - Vincenzo Librandi, Jun 24 2011

Example

sqrt(18)^2 = 18, so a(2) = 18.
sqrt(18)^3 = 76.3675323681471326352911911..., so a(3) = 76.
sqrt(18)^4 = 18^2 = 324, so a(4) = 324.
sqrt(18)^5 = 1374.61558262664838743524143993..., so a(5) = 1374.

Mathematica

Floor[Sqrt[18]^Range[0, 35]] (* Alonso del Arte, Dec 07 2017 *)

Prog

(Magma) [Floor(Sqrt(18^n)): n in [0..30]]; // Vincenzo Librandi, Jun 24 2011
(PARI) a(n)=sqrtint(18^n) \\ Charles R Greathouse IV, Nov 18 2011

Crossrefs

Cf. A001027 (bisection)

Sequence in context: A048664 A108012 A291417 * A017959 A100069 A058870

Adjacent sequences: A017955 A017956 A017957 * A017959 A017960 A017961

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved