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A189744
a(1)=4, a(2)=5, a(n) = 4*a(n-1) + 5*a(n-2).
13
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
1,1
FORMULA
G.f.: x*(4-11*x)/(1 - 4*x - 5*x^2). - Bruno Berselli, May 24 2011
MATHEMATICA
LinearRecurrence[{4, 5}, {4, 5}, 40]
PROG
(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 */
(Magma) [5/2*(-1)^(n-1)+3/2*5^(n-1): n in [1..30]]; // Vincenzo Librandi, Jul 15 2011
(PARI) a(n)=5/2*(-1)^(n-1)+3/2*5^(n-1) \\ Charles R Greathouse IV, Jul 02 2013
KEYWORD
nonn,easy
AUTHOR
Harvey P. Dale, Apr 26 2011
STATUS
approved