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 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 STATUS approved

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Last modified March 20 09:35 EDT 2023. Contains 361366 sequences. (Running on oeis4.)