|
| |
|
|
A017968
|
|
Powers of sqrt(21) rounded to nearest integer.
|
|
1
|
|
|
|
1, 5, 21, 96, 441, 2021, 9261, 42439, 194481, 891224, 4084101, 18715702, 85766121, 393029742, 1801088541, 8253624572, 37822859361, 173326116021, 794280046581, 3639848436450, 16679880978201, 76436817165460, 350277500542221, 1605173160474663, 7355827511386641
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,2
|
|
|
LINKS
|
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
|
|
|
MAPLE
|
a:= n-> round(sqrt(21)^n):
seq(a(n), n=0..25); # Alois P. Heinz, Jul 29 2022
|
|
|
MATHEMATICA
|
Floor[(Sqrt[21])^Range[0, 25]+1/2] (* Harvey P. Dale, Sep 22 2011 *)
|
|
|
PROG
|
(PARI) a(n)=round(sqrt(21)^n) \\ Charles R Greathouse IV, Nov 18 2011
(Magma) [Round(Sqrt(21)^n): n in [0..30]]; // Vincenzo Librandi, Nov 20 2011
(Python)
from math import isqrt
def A017968(n): return (m:=isqrt(k:=21**n))+int((k-m*(m+1)<<2)>=1) # Chai Wah Wu, Jul 29 2022
|
|
|
CROSSREFS
|
Cf. A010477 (sqrt(21)), A017967.
Bisection gives A009965 (even part).
Sequence in context: A343349 A159289 A201869 * A017969 A050897 A338673
Adjacent sequences: A017965 A017966 A017967 * A017969 A017970 A017971
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
N. J. A. Sloane
|
|
|
STATUS
|
approved
|
| |
|
|
