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A333992

a(n) is the multiplicative order of the n-th prime number q modulo (q-1)#.

1, 1, 2, 4, 6, 20, 60, 120, 144, 7920, 18480, 18480, 7920, 27720, 2520, 637560, 8288280, 480720240, 240360120, 480720240, 480720240, 480720240, 240360120, 9854764920, 19709529840, 9854764920, 16424608200, 670124014560, 88791431929200, 88791431929200

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OFFSET

1,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Mathoverflow, What is the multiplicative order of this number

EXAMPLE

For n = 2, q = prime(2) = 3, we have (q-1)#=2, then the multiplicative order of q modulo (q-1)# is 1.

MAPLE

with(NumberTheory):

primorial := proc(n::integer)

local total := 1:

local count := 2;

for count from 2 to n do

if isprime(count) then

total *= count

endif;

end:

return total;

end proc:

numberOfTerms := 3;

List := [seq(MultiplicativeOrder(ithprime(i), primorial(ithprime[i]-1)), i=1..numberOfTerms)]

MATHEMATICA

a[n_] := MultiplicativeOrder[Prime[n], Times @@ Prime[Range[n-1]]];

a /@ Range[30] (* Jean-François Alcover, Nov 03 2020 *)

PROG

(PARI) a(n)={znorder(Mod(prime(n), vecprod(primes(n-1))))} \\ Andrew Howroyd, Sep 05 2020

CROSSREFS

Cf. A002110.

Sequence in context: A245766 A193774 A241210 * A176652 A251724 A326363

Adjacent sequences: A333989 A333990 A333991 * A333993 A333994 A333995

KEYWORD

nonn

AUTHOR

Yassine Lagrida, Sep 04 2020

EXTENSIONS

Terms a(16) and beyond from Andrew Howroyd, Sep 05 2020

STATUS

approved

URL: https://oeis.org/A333992

⇱ A333992 - OEIS