A122149 Period of A002067 mod n.

1, 1, 1, 4, 8, 1, 3, 4, 9, 8, 10, 4, 24, 3, 8, 4, 32, 9, 18, 8, 3, 10, 22, 4

Offset: 1

Author

N. J. A. Sloane, Aug 06 2008

Keywords

• nonn
• more

Examples

			A002067 mod 5 is 1, 1, 2, 2, 4, 4, 3, 3, 1, 1, 2, 2, 4, 4, 3, 3, 1, 1, ... with period 8.
		

Crossrefs

Cf. A002067, A122159.

Programs

Mathematica

max = 40; se = Series[InverseErf[2*x/Sqrt[Pi]], {x, 0, 2*max + 1}]; a[n_] := (2*n + 1)!/2^n*Coefficient[se, x, 2*n + 1]; A002067 = Table[a[n], {n, 0, max}]; period[lst_List] := Catch[lg = If[Length[lst] <= 5, 2, 5]; lst1 = lst[[1 ;; lg]]; km = Length[lst] - lg; Do[ If[lst1 == lst[[k ;; k+lg-1]], Throw[k-1]]; If[k == km, Throw[0]], {k, 2, km}]]; Table[period[Mod[A002067, n] // Reverse], {n, 1, 24}] (* Jean-François Alcover, Dec 17 2012 *)

Extensions

Extended to 24 terms by Jean-François Alcover, Dec 17 2012