A070440 a(n) = n^2 mod 18.

0, 1, 4, 9, 16, 7, 0, 13, 10, 9, 10, 13, 0, 7, 16, 9, 4, 1, 0, 1, 4, 9, 16, 7, 0, 13, 10, 9, 10, 13, 0, 7, 16, 9, 4, 1, 0, 1, 4, 9, 16, 7, 0, 13, 10, 9, 10, 13, 0, 7, 16, 9, 4, 1, 0, 1, 4, 9, 16, 7, 0, 13, 10, 9, 10, 13, 0, 7, 16, 9, 4, 1, 0, 1, 4, 9, 16, 7, 0, 13, 10, 9, 10, 13, 0, 7, 16, 9

Offset: 0

Author

N. J. A. Sloane, May 12 2002

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000
• 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. A070441, A070442.

Programs

Mathematica

Table[Mod[n^2,18],{n,0,200}] (* Vladimir Joseph Stephan Orlovsky, Apr 23 2011 *)

PARI

a(n)=n^2%18 \\ Charles R Greathouse IV, Apr 06 2016

Formula

a(n) = a(n-18). - R. J. Mathar, Jul 27 2015

G.f.: -x*(1 +4*x +9*x^2 +16*x^3 +7*x^4 +13*x^6 +10*x^7 +9*x^8 +10*x^9 +13*x^10 +7*x^12 +16*x^13 +9*x^14 +4*x^15 +x^16) / ( (x-1)*(1+x+x^2)*(1+x^3+x^6)*(1+x)*(1-x+x^2)*(1-x^3+x^6) ). - R. J. Mathar, Jul 27 2015