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A171739
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a(n) = 2^(n*(n-1)/2)*3^(n*(n+1)/2).
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1
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1, 3, 54, 5832, 3779136, 14693280768, 342764853755904, 47976111050506371072, 40290721869103654477234176, 203018823308689211155302473269248, 6137885950748052085508841340966822477824, 1113403476497577147178633950236927694314586243072
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n+1)*a(n-1) = 6*a(n)^2.
G.f.: 1 / (1 - 6^1 / 2 * x / (1 - (6^1 - 1) * 6^1 / 2 * x / (1 - 6^2 / 2 * x / (1 - (6^2 - 1) * 6^2 / 2 * x / ... )))). - Michael Somos, Jan 03 2013
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EXAMPLE
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1 + 3*x + 54*x^2 + 5832*x^3 + 3779136*x^4 + 14693280768*x^5 + 342764853755904*x^6 + ...
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MAPLE
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MATHEMATICA
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Table[2^(n*(n-1)/2) * 3^(n*(n+1)/2), {n, 0, 20}] (* Vincenzo Librandi, Jan 03 2013 *)
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PROG
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(PARI) {a(n) = 2^(n*(n-1)/2) * 3^(n*(n+1)/2)}
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CROSSREFS
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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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