A064751 a(n) = n*5^n - 1.

4, 49, 374, 2499, 15624, 93749, 546874, 3124999, 17578124, 97656249, 537109374, 2929687499, 15869140624, 85449218749, 457763671874, 2441406249999, 12969970703124, 68664550781249, 362396240234374, 1907348632812499, 10013580322265624, 52452087402343749

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n = 1..150

Paul Leyland, Factors of Cullen and Woodall numbers

Paul Leyland, Generalized Cullen and Woodall numbers

Index entries for linear recurrences with constant coefficients, signature (11,-35,25).

Formula

G.f.: x*(4 + 5*x - 25*x^2)/((1 - 5*x)^2*(1 - x)). - Vincenzo Librandi, Jun 21 2018

a(n) = A036291(n) - 1. - Michel Marcus, Jun 21 2018

Mathematica

Table[n*5^n-1, {n, 20}] (* or *) LinearRecurrence[{11, -35, 25}, {4, 49, 374}, 20] (* Harvey P. Dale, Jun 25 2017 *)
CoefficientList[Series[(4 + 5 x - 25 x^2) / ((1 - 5 x)^2 (1 - x)), {x, 0, 33}], x] (* Vincenzo Librandi, Jun 21 2018 *)

Prog

(PARI) { for (n=1, 150, write("b064751.txt", n, " ", n*5^n - 1) ) } \\ Harry J. Smith, Sep 24 2009
(Magma) [n*5^n - 1: n in [1..30]]; // Vincenzo Librandi, Jun 21 2018

Crossrefs

Cf. A036291.

Sequence in context: A113525 A290263 A224538 * A045787 A067474 A053769

Adjacent sequences: A064748 A064749 A064750 * A064752 A064753 A064754

Keyword

nonn

Author

N. J. A. Sloane, Oct 19 2001

Status

approved