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A093451
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Number of distinct prime divisors of Product(k, k=1+(n-1)n/2..n(n+1)/2) (i.e. of 1, 2*3, 4*5*6, 7*8*9*10, ...).
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2
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0, 2, 3, 4, 6, 6, 7, 8, 10, 10, 11, 13, 13, 14, 16, 15, 18, 17, 20, 19, 22, 21, 22, 24, 24, 26, 26, 27, 30, 28, 30, 31, 32, 33, 33, 36, 35, 36, 38, 39, 39, 39, 43, 41, 43, 44, 44, 47, 45, 49, 48, 48, 52, 49, 53, 53, 54, 54, 55, 58, 55, 60, 59, 59, 62, 60, 65, 64, 64, 65, 66, 68
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| a(7) = 7 as the prime divisors of the product 22*23*24*25*26*27*28 are 2,3,5,7,11,13 and 23.
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MAPLE
| with(numtheory): a:=n->nops(factorset(product(k, k=1+n*(n-1)/2..n*(n+1)/2))): seq(a(n), n=1..80); (Deutsch)
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CROSSREFS
| Sequence in context: A075527 A154257 A060019 * A106006 A050460 A175808
Adjacent sequences: A093448 A093449 A093450 * A093452 A093453 A093454
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 03 2004
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EXTENSIONS
| Corrected and extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 05 2006
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