A246408 Nonnegative integers k satisfying sec(k) < sec(k+1) > sec(k+2).

0, 2, 4, 6, 8, 10, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 122, 124, 126, 128

Offset

1,2

Comments

A246407, A246408, and A246409 partition the nonnegative integers.

Links

Clark Kimberling, Table of n, a(n) for n = 1..1000

Mathematica

z = 500; f[x_] := f[x] = Sec[x];
Select[Range[0, z], f[#] > f[# + 1] &]  (* A246407 *)
Select[Range[0, z], f[#] < f[# + 1] > f[# + 2] &]  (* A246408 *)
Select[Range[0, z], f[#] < f[# + 1] < f[# + 2] > f[# + 3] &]  (* A246409 *)
Join[{0}, Position[Partition[Sec[Range[130]], 3, 1], _?(#[[1]] <#[[2]]> #[[3]]&), 1, Heads->False]//Flatten] (* Harvey P. Dale, Nov 19 2018 *)

Crossrefs

Cf. A246407, A246409.

Sequence in context: A334292 A085884 A246404 * A182766 A329828 A172278

Adjacent sequences: A246405 A246406 A246407 * A246409 A246410 A246411

Keyword

nonn,easy

Author

Clark Kimberling, Aug 25 2014

Status

approved