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A060377 Pepin's test numbers. 1
3, 9, 6561, 11790184577738583171520872861412518665678211592275841109096961 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Next two terms have 15635 and 1024610093 digits respectively. [Corrected by Michael S. Branicky and Sean A. Irvine, Nov 12 2022]

LINKS

Table of n, a(n) for n=0..3.

C. K. Caldwell, Pepin's Test

FORMULA

a(n) = 3^((F(n)-1)/2) where F(n) is a Fermat number (A000215).

EXAMPLE

a(1) = 3^((F(1)-1)/2) = 3^((5-1)/2) = 3^2 = 9.

PROG

(Python)

def a(n): return 3**(2**(2**n-1))

print([a(n) for n in range(4)]) # Michael S. Branicky, Nov 12 2022

CROSSREFS

Sequence in context: A060712 A122463 A072005 * A255503 A027896 A116620

Adjacent sequences: A060374 A060375 A060376 * A060378 A060379 A060380

KEYWORD

nonn

AUTHOR

Jason Earls, Apr 02 2001

EXTENSIONS

Corrected offset, formula and example Harry J. Smith, Jul 04 2009

STATUS

approved

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Last modified February 5 15:20 EST 2023. Contains 360086 sequences. (Running on oeis4.)