login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245972 Tower of 5s mod n. 9
0, 1, 2, 1, 0, 5, 3, 5, 2, 5, 1, 5, 5, 3, 5, 5, 14, 11, 6, 5, 17, 1, 5, 5, 0, 5, 2, 17, 9, 5, 25, 21, 23, 31, 10, 29, 35, 25, 5, 5, 9, 17, 28, 1, 20, 5, 23, 5, 45, 25, 14, 5, 51, 29, 45, 45, 44, 9, 48, 5, 14, 25, 38, 53, 5, 23, 5, 65, 5, 45, 1, 29, 34, 35, 50 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = (5^(5^(5^(5^(5^ ... ))))) mod n, provided sufficient 5s are in the tower such that adding more doesn't affect the value of a(n).

LINKS

Wayne VanWeerthuizen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = 5^a(A000010(n)) mod n. For n<=18, a(n)=(5^5) mod n.

EXAMPLE

a(2) = 1, as 5^X is odd for any whole number X.

a(19) = 6, as 5^(5^5) == 5^(5^(5^5)) == 5^(5^(5^(5^5))) == 6 (mod 19).

MAPLE

A:= proc(n) option remember; 5 &^ A(numtheory:-phi(n)) mod n end proc:

A(2):= 1;

seq(A(n), n=2..100);

PROG

(Sage)

def a(n):

    if ( n <= 18 ):

        return 3125%n

    else:

        return power_mod(5, a(euler_phi(n)), n)

CROSSREFS

Cf. A240162, A245970, A245971, A245973, A245974.

Sequence in context: A327358 A256664 A226783 * A088391 A128899 A155887

Adjacent sequences:  A245969 A245970 A245971 * A245973 A245974 A245975

KEYWORD

nonn,easy

AUTHOR

Wayne VanWeerthuizen, Aug 08 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 29 17:41 EDT 2021. Contains 346346 sequences. (Running on oeis4.)