A353584 Denominators of coefficients c(n) in product expansion of 1 + tan x = Product_{k>=1} 1 + c(k)*x^k.

1, 1, 3, 3, 15, 15, 315, 105, 567, 405, 155925, 467775, 1216215, 34749, 638512875, 638512875, 2170943775, 32564156625, 1856156927625, 3093594879375, 38979295480125, 5568470782875, 49308808782358125, 2900518163668125, 284473896821296875, 1232720219558953125

Offset

1,3

Comments

See the sequence of numerators, A353583, for references and more.

Links

Table of n, a(n) for n=1..26.

Example

1 + tan x = (1 + x)(1 + 1/3*x^3)(1 - 1/3*x^4/3)(1 + 7/15*x^5)(1 - 7/15*x^5)(...),
and this sequence lists the denominators of (1, 0, 1/3, -1/3, 7/15, -7/15, ...).

Prog

(PARI) t=1+tan(x+O(x)^29); vector(#t-1, n, c=polcoef(t, n); t/=1+c*x^n; denominator(c))

Crossrefs

Cf. A353583 (numerators)

Cf. A170918 / A170919 for a variant.

Sequence in context: A055634 A133221 A232097 * A110096 A157526 A208229

Adjacent sequences: A353581 A353582 A353583 * A353585 A353586 A353587

Keyword

nonn,frac

Author

M. F. Hasler, May 07 2022

Status

approved