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A189734
a(1)=2, a(2)=5, a(n)=2*a(n-1) + 5*a(n-2).
13
2, 5, 20, 65, 230, 785, 2720, 9365, 32330, 111485, 384620, 1326665, 4576430, 15786185, 54454520, 187839965, 647952530, 2235104885, 7709972420, 26595469265, 91740800630, 316458947585, 1091621898320, 3765538534565, 12989186560730, 44806065794285
OFFSET
1,1
FORMULA
G.f.: x*(2+x)/(1-2*x-5*x^2). - Bruno Berselli, May 24 2011
MATHEMATICA
LinearRecurrence[{2, 5}, {2, 5}, 40]
PROG
(Maxima) a[1]:2$ a[2]:5$ a[n]:=2*a[n-1]+5*a[n-2]$ makelist(a[n], n, 1, 26); /* Bruno Berselli, May 24 2011 */
KEYWORD
nonn
AUTHOR
Harvey P. Dale, Apr 26 2011
STATUS
approved