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2, 6, 12, 60, 300, 2100, 21000, 252000, 4284000, 94248000, 2733192000, 106594488000, 5436318888000, 369669684384000, 33270271594560000, 3959162319752640000, 625547646520917120000, 130739458122871678080000, 36214829900035454828160000
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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2,1
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LINKS
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FORMULA
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a(n) ~ c * r^(n*(n+1)/2), where r = A060006 = 1.324717957244746025960908854478... is the root of the equation r^3 = r + 1, c = 0.81845731383668335747954234022593868885066763327809025622515304041339344876... .
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MATHEMATICA
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Table[Product[SeriesCoefficient[(3-x^2)/(1-x^2-x^3), {x, 0, k}], {k, 2, n}], {n, 2, 20}]
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PROG
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(Python)
A254232_list, a, b, c, d = [2], 3, 0, 2, 2
for _ in range(200):
a, b, c = b, c, a+b
d *= c
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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