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%I #4 Oct 15 2014 20:54:47
%S 1,2,3,5,7,9,11,13,16,19,22,25,28,32,36,40,44,48,53,58,63,68,73,78,84,
%T 90,96,102,109,116,123,130,137,144,152,160,168,176,184,193,202,211,
%U 220,229,239,249,259,269,279,290,301,311,323,334,345,357,369,381,393,406,419,431,445,458,471,485,499,513,527,541
%N Numbers k such that A248418(k+1) = A248418(k) + 1.
%C Complement of A248419.
%H Clark Kimberling, <a href="/A248420/b248420.txt">Table of n, a(n) for n = 1..100</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, A248419, A248421.
%K nonn,easy
%O 1,2
%A _Clark Kimberling_, Oct 07 2014
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