A204695 a(n) = n^n (mod 9).

1, 1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0, 1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0, 1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0, 1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0, 1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7

Offset: 0

Author

José María Grau Ribas, Jan 18 2012

Keywords

• nonn
• easy

Comments

For n>0, periodic with period 18 = A174824(9): repeat [1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0].

Links

• Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

Crossrefs

Cf. A000312, A174824.

Programs

Mathematica

Table[PowerMod[n,n,9], {n,0,100}]
Join[{1},LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},{1, 4, 0, 4, 2, 0, 7, 1, 0, 1, 5, 0, 4, 7, 0, 7, 8, 0},86]] (* Ray Chandler, Aug 27 2015 *)

PARI

a(n)=lift(Mod(n,9)^n) \\ Charles R Greathouse IV, Jan 23 2012

Formula

G.f.: (x^18 - 8*x^17 - 7*x^16 - 7*x^14 - 4*x^13 - 5*x^11 - x^10 - x^8 - 7*x^7 - 2*x^5 - 4*x^4 - 4*x^2 - x - 1)/(x^18 - 1). - Chai Wah Wu, Jun 04 2016

a(n) = A000312(n) mod 9. - Michel Marcus, Jun 04 2016