A053793 n^2+n modulo 7.

0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0, 0, 2, 6, 5, 6, 2, 0

Offset: 0

Author

Stuart M. Ellerstein (ellerstein(AT)aol.com), Mar 27 2000

Keywords

• nonn
• easy

Comments

Pronic residues (mod m) are analogous to quadratic residues.

Periodic with period 7.

Links

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

Programs

Mathematica

Table[Mod[n^2+n,7],{n,0,120}] (* Harvey P. Dale, Aug 26 2012 *)
LinearRecurrence[{0, 0, 0, 0, 0, 0, 1},{0, 2, 6, 5, 6, 2, 0},105] (* Ray Chandler, Aug 26 2015 *)

PARI

A053793(n)=[0, 2, 6, 5, 6, 2, 0][n%7+1] \\ - M. F. Hasler, Aug 27 2012

Extensions

More terms from James Sellers, Apr 08 2000