A083529 a(n) = 5^n mod 3*n.

2, 1, 8, 1, 5, 1, 5, 1, 26, 25, 5, 1, 5, 25, 35, 1, 5, 1, 5, 25, 62, 25, 5, 1, 50, 25, 80, 37, 5, 55, 5, 1, 26, 25, 80, 1, 5, 25, 8, 25, 5, 1, 5, 97, 80, 25, 5, 1, 68, 25, 125, 1, 5, 1, 155, 25, 125, 25, 5, 145, 5, 25, 188, 1, 5, 181, 5, 13, 125, 205, 5, 1, 5, 25, 125, 169, 80, 181, 5

Offset: 1

Author

Labos Elemer, Apr 30 2003

Keywords

• easy
• nonn

Comments

From Robert Israel, Dec 25 2014: (Start)

a(n) == (-1)^n mod 3.

a(n) = 1 if and only if n is even and in A067946.

For n > 3, a(n) = 5 if and only if n is odd and in A123091. (End)

Examples

			a(3) = 8 because 5^3 = 125 and 125 mod (3 * 3) = 8.
a(4) = 1 because 5^4 = 625 and 625 mod (3 * 4) = 1.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000079, A000244, A000351, A000420, A082511, A083528, A083530, A067946, A123091.

Programs

Magma

[Modexp(5, n, 3*n): n in [1..80]]; // Vincenzo Librandi, Oct 19 2018

Maple

seq(5 &^n mod 3*n, n = 1 .. 1000); # Robert Israel, Dec 25 2014

Mathematica

Table[Mod[5^w, 3 * w], {w, 100}]
Table[PowerMod[5, n, 3n], {n, 80}] (* Harvey P. Dale, Jul 26 2014 *)

PARI

a(n)=lift(Mod(5,3*n)^n) \\ Charles R Greathouse IV, Oct 03 2016