A070450 a(n) = n^2 mod 28.

0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25, 8, 21, 8, 25, 16, 9, 4, 1, 0, 1, 4, 9, 16

Offset: 0

Author

N. J. A. Sloane, May 12 2002

Keywords

• nonn
• easy

Comments

Periodic, with period = 14. - Harvey P. Dale, Jul 20 2021

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, 1).

Crossrefs

Cf. A070448, A070449.

Programs

Mathematica

Table[Mod[n^2,28],{n,0,200}] (* Vladimir Joseph Stephan Orlovsky, Apr 27 2011 *)
PowerMod[Range[0,100],2,28] (* or *) PadRight[{},100,{0,1,4,9,16,25,8,21,8,25,16,9,4,1}] (* Harvey P. Dale, Jul 20 2021 *)

PARI

a(n)=n^2%28 \\ Charles R Greathouse IV, Apr 06 2016

Formula

a(n) = a(n-28). - G. C. Greubel, Mar 24 2016