A017967 Powers of sqrt(21) rounded down.

1, 4, 21, 96, 441, 2020, 9261, 42439, 194481, 891223, 4084101, 18715701, 85766121, 393029741, 1801088541, 8253624572, 37822859361, 173326116021, 794280046581, 3639848436450, 16679880978201, 76436817165460

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..700

Formula

a(n) = floor(sqrt(21^n)). - Vincenzo Librandi, Jun 24 2011

Mathematica

Floor[(Sqrt[21])^Range[0, 30]] (* Harvey P. Dale, May 08 2018 *)

Prog

(Magma) [Floor(Sqrt(21^n)): n in [0..30]]; // Vincenzo Librandi, Jun 24 2011
(PARI) a(n)=sqrtint(21^n) \\ Charles R Greathouse IV, Nov 18 2011

Crossrefs

Cf. A010477 (sqrt(21)).

Sequence in context: A371309 A220574 A231377 * A292308 A076901 A080043

Adjacent sequences: A017964 A017965 A017966 * A017968 A017969 A017970

Keyword

nonn

Author

N. J. A. Sloane

Status

approved