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Search: id:A094342
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| A094342 |
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Successive record-setters for tau(n+1)*tau(n-1)/tau(n)^2, where tau(n) is the number of divisors of n. |
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+0
1
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| 3, 5, 7, 11, 17, 19, 29, 41, 71, 181, 239, 379, 449, 701, 881, 1429, 1871, 2729, 3079, 4159, 10529, 11969, 23561, 40699, 51679, 90271, 104651, 146719, 226799, 244529, 252449, 388961, 403649
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Most terms are primes. These are numbers with few factors which are sandwiched between numbers with many factors. Terms <379 are same as those of A090481.
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EXAMPLE
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tau(16)*tau(18)/tau(17)^2 = 5*6/2^2 = 15/2 and this is larger than for any n < 17, so 17 is in the sequence.
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MAPLE
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f := x -> tau(x-1)*tau(x+1)/tau(x)^2:?print m := 1: A := []: for k from 2 to 10^6 do if f(k) > m then m := f(k): A := [op(A), [k, f(k)]]: fi; od;
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CROSSREFS
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Cf. A090481.
Sequence in context: A155489 A045396 A155779 this_sequence A045397 A152998 A144574
Adjacent sequences: A094339 A094340 A094341 this_sequence A094343 A094344 A094345
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KEYWORD
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easy,nonn
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AUTHOR
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Isabel C. Lugo (isabel(AT)mit.edu), Jun 04 2004
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