A248419 - OEIS

%I #4 Oct 15 2014 20:54:31

%S 4,6,8,10,12,14,15,17,18,20,21,23,24,26,27,29,30,31,33,34,35,37,38,39,

%T 41,42,43,45,46,47,49,50,51,52,54,55,56,57,59,60,61,62,64,65,66,67,69,

%U 70,71,72,74,75,76,77,79,80,81,82,83,85,86,87,88,89,91

%N Numbers k such that A248418(k+1) = A248418(k).

%C Complement of A248420.

%H Clark Kimberling, <a href="/A248419/b248419.txt">Table of n, a(n) for n = 1..1000</a>

%e A248418 = (1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, ...), so that A248419 = (4,6,8,10,12,14,15, ...) and A248420 = (1, 2, 3, 5, 7, 9, 11, 13, 16, 19, 22, 25, ...).

%t z = 550; p[k_] := p[k] = k*Tan[Pi/k]; N[Table[p[n] - Pi, {n, 3, z/10}]]

%t f[n_] := f[n] = Select[2 + Range[z], p[#] - Pi < 1/n &, 1];

%t u = Flatten[Table[f[n], {n, 3, z}]]  (* A248418 *)

%t Differences[u]

%t v = Flatten[Position[Differences[u], 0]]    (* A248419 *)

%t w = Flatten[Position[Differences[u], 1]]    (* A248420 *)

%t g = Table[Floor[1/(p[n] - Pi)], {n, 3, z}]  (* A248421 *)

%Y Cf. A248418, A248420, A248421.

%K nonn,easy

%O 1,1

%A _Clark Kimberling_, Oct 07 2014