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A372944
Numbers k that divide the k-th tangent (or "zag") number.
0
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.
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
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, May 17 2024
STATUS
approved