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A328604
G.f.: (1 + 7*x) / (1 - 2*x - 9*x^2).
3
1, 9, 27, 135, 513, 2241, 9099, 38367, 158625, 662553, 2752731, 11468439, 47711457, 198638865, 826680843, 3441111471, 14322350529, 59614704297, 248130563355, 1032793465383, 4298762000961, 17892665190369, 74474188389387, 309982363492095, 1290232422488673, 5370306116406201
OFFSET
0,2
FORMULA
a(n) = 2*a(n-1) + 9*a(n-2) for n>1. - Colin Barker, Oct 21 2019
a(n)/a(n-1) ~ 1 + sqrt(10).
PROG
(PARI) Vec((1 + 7*x) / (1 - 2*x - 9*x^2) + O(x^30)) \\ Colin Barker, Dec 13 2019
CROSSREFS
Sequence in context: A126322 A020279 A339725 * A357667 A230185 A340235
KEYWORD
nonn,easy
AUTHOR
Kyle MacLean Smith, Oct 20 2019
EXTENSIONS
Edited by N. J. A. Sloane, Dec 05 2019
STATUS
approved