A025986 Expansion of 1/((1-2x)(1-5x)(1-6x)(1-7x)).

1, 20, 257, 2704, 25389, 221676, 1841449, 14758568, 115171397, 880623172, 6627177921, 49248518592, 362296167325, 2643446894108, 19158543110873, 138087153497176, 990728497913973, 7081081591668084

Offset

0,2

Links

Table of n, a(n) for n=0..17.

Index entries for linear recurrences with constant coefficients, signature (20,-143,424,-420).

Formula

a(n) = -2*2^n/15 + 125*5^n/6 - 54*6^n/1 + 343*7^n/10. - R. J. Mathar, Jun 20 2013

E.g.f.: exp(2*x)*(1029*exp(5*x) - 1620*exp(4*x) + 625*exp(3*x) - 4)/30. - Stefano Spezia, Sep 29 2022

Mathematica

CoefficientList[Series[1/((1-2x)(1-5x)(1-6x)(1-7x)), {x, 0, 20}], x] (* or *) LinearRecurrence[{20, -143, 424, -420}, {1, 20, 257, 2704}, 20] (* Harvey P. Dale, Oct 10 2017 *)

Crossrefs

Cf. A028027, A028032.

Sequence in context: A075469 A028032 A348055 * A028027 A268764 A081244

Adjacent sequences: A025983 A025984 A025985 * A025987 A025988 A025989

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved