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A316661 a(n) = ceiling(sqrt((2*n)^n)). 0
1, 2, 4, 15, 64, 317, 1728, 10268, 65536, 445376, 3200000, 24172677, 191102976, 1575167570, 13492928512, 119786923327, 1099511627776, 10412878353557, 101559956668416, 1018460448140641, 10485760000000000, 110692335104026964, 1196683881290399744 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(0)=1 relies on the algebraic identity 0^0 = 1 (à la Knuth).

LINKS

Table of n, a(n) for n=0..22.

D. E. Knuth, Two Notes on Notation, The American Mathematical Monthly, 99 (1992), 403-422.

MATHEMATICA

Join[{1}, Table[Ceiling[Sqrt[(2 n)^n]], {n, 30}]] (* Vincenzo Librandi, Jul 10 2018 *)

PROG

(PARI) a(n) = ceil(sqrt((2*n)^n)); \\ Michel Marcus, Jul 10 2018

(MAGMA) [Ceiling(Sqrt((2*n)^n)): n in [0..25]]; // Vincenzo Librandi, Jul 10 2018

CROSSREFS

Cf. A242764.

Sequence in context: A243796 A153939 A112281 * A014517 A020110 A290024

Adjacent sequences:  A316658 A316659 A316660 * A316662 A316663 A316664

KEYWORD

nonn,easy

AUTHOR

Greg Huber, Jul 09 2018

STATUS

approved

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Last modified May 16 15:55 EDT 2021. Contains 343949 sequences. (Running on oeis4.)