A027475 a(n) = (n-1) * 15^(n-2).

1, 30, 675, 13500, 253125, 4556250, 79734375, 1366875000, 23066015625, 384433593750, 6343154296875, 103797070312500, 1686702392578125, 27246730957031250, 437893890380859375, 7006302246093750000

Offset

2,2

Comments

Second column of A027467.

Links

Vincenzo Librandi, Table of n, a(n) for n = 2..200

Index entries for linear recurrences with constant coefficients, signature (30,-225).

Formula

Numerators of sequence a[2,n] in (a[i,j])^4 where a[i,j] = binomial(i-1, j-1)/2^(i-1) if j<=i, 0 if j>i.

G.f.: x^2/(1 - 15*x)^2. - Vincenzo Librandi, Jul 16 2018

a(2) = 1, a(3) = 30; for n >= 4, a(n) = 30*a(n-1) - 225*a(n-2). - Jianing Song, Jul 16 2018

Maple

seq((n-1)*15^(n-2), n=2..50); # Muniru A Asiru, Jul 15 2018

Mathematica

a[n_]:= n 15^(n-1); a[Range[40]] (* Vladimir Joseph Stephan Orlovsky, Feb 09 2011 *)
CoefficientList[Series[x^2/(1-15x)^2, {x, 0, 33}], x] (* Vincenzo Librandi, Jul 16 2018 *)

Prog

(Magma) [(n-1)*15^(n-2): n in [2..50]]; // Vincenzo Librandi, Dec 29 2012
(GAP) List([2..50], n->(n-1)*15^(n-2)); # Muniru A Asiru, Jul 15 2018
(Sage) [15^(n-2)*(n-1) for n in (2..50)] # G. C. Greubel, May 14 2021

Crossrefs

Cf. A027467.

Sequence in context: A075473 A051563 A152499 * A180801 A035520 A122186

Adjacent sequences: A027472 A027473 A027474 * A027476 A027477 A027478

Keyword

nonn,easy

Author

Olivier Gérard

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 17 2005

Status

approved