A104686 a(n) = n*(n+1)/2 (mod 6).

0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3, 0, 4, 3, 3, 4, 0, 3, 1, 0, 0, 1, 3

Offset: 0

Author

Stuart M. Ellerstein (ellerstein(AT)aol.com), Apr 22 2005

Keywords

• easy
• nonn

Links

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

Programs

Mathematica

Table[Mod[(n^2 + n)/2, 6], {n, 0, 100}] (* Arkadiusz Wesolowski, Nov 28 2011 *)
Mod[Accumulate[Range[0,90]],6] (* or *) LinearRecurrence[{0,0,1,0,0,-1,0,0,1},{0,1,3,0,4,3,3,4,0},90] (* Harvey P. Dale, Aug 21 2022 *)

Formula

a(n) = A010875(A000217(n)). - Arkadiusz Wesolowski, Nov 28 2011

G.f.: -x*(1+3*x+3*x^3+3*x^5+x^6) / ( (x-1)*(1+x+x^2)*(x^2+1)*(x^4-x^2+1) ). - R. J. Mathar, Oct 16 2015