A189744 a(1)=4, a(2)=5, a(n) = 4*a(n-1) + 5*a(n-2).

4, 5, 40, 185, 940, 4685, 23440, 117185, 585940, 2929685, 14648440, 73242185, 366210940, 1831054685, 9155273440, 45776367185, 228881835940, 1144409179685, 5722045898440, 28610229492185, 143051147460940, 715255737304685, 3576278686523440, 17881393432617185

Offset: 1

Author

Harvey P. Dale, Apr 26 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..500
• Index entries for linear recurrences with constant coefficients, signature (4,5).

Crossrefs

Cf. A000045, A000079, A105476, A159612, A080040, A135522, A103435, A189732, A189734-A189739, A189741, A189742, A189743, A189745-A189749.

Programs

Magma

[5/2*(-1)^(n-1)+3/2*5^(n-1): n in [1..30]]; // Vincenzo Librandi, Jul 15 2011

Mathematica

LinearRecurrence[{4,5},{4,5},40]

Maxima

a[1]:4$ a[2]:5$ a[n]:=4*a[n-1]+5*a[n-2]$ makelist(a[n], n, 1, 24); /* Bruno Berselli, May 24 2011 */

PARI

a(n)=5/2*(-1)^(n-1)+3/2*5^(n-1) \\ Charles R Greathouse IV, Jul 02 2013

Formula

G.f.: x*(4-11*x)/(1 - 4*x - 5*x^2). - Bruno Berselli, May 24 2011