A372944 Numbers k that divide the k-th tangent (or "zag") number.

1, 2, 4, 8, 16, 32, 64, 68, 128, 256, 512, 592, 1024, 1156, 2048, 2056, 4096, 4112, 8192, 8224, 8576, 10928, 16384, 16448, 19652, 20512, 28936, 32768, 37888, 41024, 43882, 64804, 65536, 82048

Offset

1,2

Comments

Numbers k such that k | A000182(k).

All the powers of 2 are terms.

Links

Table of n, a(n) for n=1..34.

Example

2 is a term since A000182(2) = 2 is divisible by 2.
4 is a term since A000182(4) = 272 = 4 * 68 is divisible by 4.

Mathematica

Select[Range[1000], Divisible[((-4)^# - (-16)^#) * BernoulliB[2*#]/(2*#), #] &]

Prog

(PARI) is(n) = (((-4)^n - (-16)^n) * bernfrac(2*n) / (2*n)) % n == 0;

Crossrefs

Cf. A000182.

Similar sequences: A014847 (Catalan), A016089 (Lucas), A023172 (Fibonacci), A051177 (partition), A232570 (tribonacci), A246692 (Pell), A266969 (Motzkin).

Sequence in context: A036135 A036131 A115424 * A225878 A323097 A272985

Adjacent sequences: A372941 A372942 A372943 * A372945 A372946 A372947

Keyword

nonn,more

Author

Amiram Eldar, May 17 2024

Status

approved