A248609 Numbers k such that A248607(k+1) = A248607(k) + 2.

2, 4, 6, 8, 10, 12, 14, 16, 18, 19, 21, 23, 25, 27, 28, 30, 32, 34, 36, 37, 39, 41, 43, 44, 46, 48, 50, 51, 53, 55, 57, 58, 60, 62, 64, 65, 67, 69, 71, 72, 74, 76, 78, 79, 81, 83, 84, 86, 88, 90, 91, 93, 95, 97, 98, 100, 102, 104, 105, 107, 109, 110, 112

Offset: 1

Author

Clark Kimberling, Oct 10 2014

Keywords

• nonn
• easy

Examples

			(A248607(k+1) - A248607(k)) = (1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2,...), so that A248608 = (1, 3, 5, 7, 9, 11, 13, 15, 17, ..) and A248567 = (2, 4, 6, 8, 10, 12, 14, 16, ...).
		

Links

• Clark Kimberling, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A248607, A248608, A248611.

Programs

Mathematica

z = 300; p[k_] := p[k] = Sum[2^h/((2 h + 1) Binomial[2 h, h]), {h, 0, k}]
d = N[Table[Pi/2 - p[k], {k, 1, z/5}], 12]
f[n_] := f[n] = Select[Range[z], Pi/2 - p[#] < 1/3^n &, 1]
u = Flatten[Table[f[n], {n, 1, z}]]  (* A248607 *)
d = Differences[u]
v = Flatten[Position[d, 1]] (* A248608 *)
w = Flatten[Position[d, 2]] (* A248609 *)