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A027873
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a(n) = Product_{i=1..n} (6^i - 1).
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18
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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) ~ c * 6^(n*(n+1)/2), where c = Product_{k>=1} (1-1/6^k) = A132034 = 0.805687728162164940923750215496298968917997628693... . - Vaclav Kotesovec, Nov 21 2015
a(n) = 6^(binomial(n+1,2))*(1/6;1/6)_{n}, where (a;q)_{n} is the q-Pochhammer symbol. - G. C. Greubel, Dec 24 2015
G.f.: Sum_{n>=0} 6^(n*(n+1)/2)*x^n / Product_{k=0..n} (1 + 6^k*x). - Ilya Gutkovskiy, May 22 2017
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MATHEMATICA
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Table[Product[(6^k-1), {k, 1, n}], {n, 0, 20}] (* Vaclav Kotesovec, Jul 17 2015 *)
FoldList[Times, Join[{1}, 6^Range[10]-1]] (* Harvey P. Dale, Oct 13 2017 *)
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PROG
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(Magma) [1] cat [&*[ 6^k-1: k in [1..n] ]: n in [1..11]]; // Vincenzo Librandi, Dec 24 2015
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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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