A246692 Numbers k such that k | A000129(k).

1, 2, 4, 8, 12, 16, 24, 32, 36, 48, 60, 64, 72, 84, 96, 108, 120, 128, 132, 136, 144, 168, 180, 192, 216, 240, 252, 256, 264, 272, 288, 300, 324, 336, 360, 384, 396, 408, 420, 432, 480, 504, 512, 528, 540, 544, 576, 588, 600, 648, 660, 672, 720, 756, 768

Offset: 1

Author

Clark Kimberling, Sep 01 2014

Keywords

• nonn
• easy

Comments

These are the numbers k such that mean of the k-th row of the Delannoy triangle at A027926 is an integer. All such k except 0 and 1 are multiples of 4.

Is A181824 a subsequence? The first 31 terms appear in this sequence. - Jaycob Coleman, Mar 08 2015 [The first 323 terms of A181824 appear in this sequence. - Amiram Eldar, Mar 31 2021]

Examples

			Row 4 of the Delannoy triangle is (1,5,5,1), with sum 12 = A000129(4) divisible by 4.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A246693, A000129, A027926.

Cf. A181824.

Programs

Mathematica

z = 1000; t = LinearRecurrence[{2, 1}, {1, 2}, z]; (* A000129 *)
Select[Range[1, z], IntegerQ[t[[#]]/#] &]   (* A246692 *)
Table[t[[u[[n]]]]/u[[n]], {n, 1, 17}]  (* A246693 *)