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Search: id:A084678
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| A084678 |
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a(n)=b(n,n) with b(n,1)=n and b(n,k)=binomial(b(n,k-1),d(n,n-k+1)) for 1<k<=n, where d(n,i) are the divisors of n, d(i)<d(j), 1<=i<j<=A000005(n). |
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1
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| 1, 2, 3, 6, 5, 190, 7, 2415, 84, 31626, 11, 10485409451852020512869123005636410508621081799664615969238750, 13, 5887596, 4509005501, 652786136966869378239977875665, 17
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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n>1: a(n) = n iff n is prime;
a(18) > 10^150.
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EXAMPLE
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Set of divisors of n=10: {1,2,5,10}, binomial(10,5)=252 ->
binomial(252,2)=31626 -> binomial(31626,1)=31626=a(10).
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CROSSREFS
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Sequence in context: A156833 A124655 A066838 this_sequence A102402 A124498 A113399
Adjacent sequences: A084675 A084676 A084677 this_sequence A084679 A084680 A084681
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 28 2003
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