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A181574
a(n) = Product_{i=2..n} (tau(i)+1)/(tau(i)-1), where tau(.)=A000005(.).
1
1, 3, 9, 18, 54, 90, 270, 450, 900, 1500, 4500, 6300, 18900, 31500, 52500, 78750, 236250, 330750, 992250, 1389150, 2315250, 3858750, 11576250, 14883750, 29767500, 49612500, 82687500, 115762500, 347287500, 446512500, 1339537500, 1875352500, 3125587500
OFFSET
1,2
COMMENTS
The value of the empty product at n=1 is 1.
Partial products of the sequence of fractions 3, 3, 2, 3, 5/3, 3, 5/3, 2, 5/3, 3, 7/5, ...
The sequence is declared "fini" because the products are no longer integers at n >= 72.
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..71 (full sequence)
MAPLE
A181574 := proc(n) mul( (numtheory[tau](i)+1)/(numtheory[tau](i)-1) , i=2..n) ; end proc; # R. J. Mathar, Feb 01 2011
MATHEMATICA
FoldList[Times, 1, (# + 1)/(# - 1) & /@ Array[DivisorSigma[0, #] &, 70, 2]] (* Amiram Eldar, Apr 17 2024 *)
CROSSREFS
Cf. A000005.
Sequence in context: A015656 A188797 A056372 * A101652 A026565 A174470
KEYWORD
nonn,easy,fini,full
AUTHOR
Ctibor O. Zizka, Jan 30 2011
STATUS
approved