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Search: id:A072512
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| A072512 |
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Product of all n - d, where 1 < d < n and d is a divisor of n. |
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+0
2
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| 1, 1, 1, 2, 1, 12, 1, 24, 6, 40, 1, 4320, 1, 84, 120, 1344, 1, 25920, 1, 43200, 252, 220, 1, 31933440, 20, 312, 432, 183456, 1, 136080000, 1, 322560, 660, 544, 840, 12563527680, 1, 684, 936, 919296000, 1, 1155772800, 1, 1219680, 1814400, 1012, 1
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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If n is prime then a(n) = 1.
If n is not a prime or a prime square then n divides a(n).
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EXAMPLE
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For n = 16 the nontrivial divisors d are 2,4 and 8, so a(16) = (16-2)*(16-4)*(16-8) = 14*12*8 = 1344.
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PROGRAM
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(PARI) for(n=1, 47, d=divisors(n); print1(prod(j=2, matsize(d)[2]-1, n-d[j]), ", "))
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CROSSREFS
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Cf. A072513.
Sequence in context: A128247 A105608 A051190 this_sequence A118588 A058734 A103187
Adjacent sequences: A072509 A072510 A072511 this_sequence A072513 A072514 A072515
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 28 2002
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Jul 31 2002
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