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13, 39, 117, 351, 1053, 3159, 9477, 28431, 85293, 255879, 767637, 2302911, 6908733, 20726199, 62178597, 186535791, 559607373, 1678822119, 5036466357, 15109399071, 45328197213, 135984591639, 407953774917, 1223861324751, 3671583974253, 11014751922759
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OFFSET
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0,1
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COMMENTS
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Also maximum leaf number of the (n+3)-Apollonian network for n >= 0. - Eric W. Weisstein, Jan 17 2018
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LINKS
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FORMULA
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G.f.: 13/(1-3*x).
a(n) = 3*a(n-1).
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MATHEMATICA
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Table[13 3^n, {n, 0, 30}]
CoefficientList[Series[13/(1 - 3 x), {x, 0, 20}], x] (* Eric W. Weisstein, Jan 17 2018 *)
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PROG
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(Magma) [13*3^n: n in [0..30]];
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CROSSREFS
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Cf. k*3^n: A000244 (k=1,3,9), A008776 (k=2,6), A003946 (k=4), A005030 (k=5), A005032 (k=7), A005051 (k=8), A005052 (k=10), A120354 (k=11), A003946 (k=12), this sequence (k=13), A258598 (k=17), A176413 (k=19).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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