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A072486
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a(1) = 1, a(n) = a(n-1) times smallest prime factor of n.
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4
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1, 2, 6, 12, 60, 120, 840, 1680, 5040, 10080, 110880, 221760, 2882880, 5765760, 17297280, 34594560, 588107520, 1176215040, 22348085760, 44696171520, 134088514560, 268177029120, 6168071669760, 12336143339520, 61680716697600
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n) = product of the smallest divisors > 1 of all the numbers from 2 to n.
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EXAMPLE
| a(5) = 60. a(6) = 1*2*3*2*5*2 = 120. Also a(6) = a(5) * 2 = 120.
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PROG
| (PARI) al(n)=local(v=vector(n)); v[1]=1; for(k=2, n, v[k]=v[k-1]*factor(k)[1, 1]); v \\ Franklin T. Adams-Watters, Jan 13 2012
(PARI) A072486(n)=prod(k=2, n, factor(k)[1, 1]) \\ - M. F. Hasler, Jan 13 2012
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CROSSREFS
| Cf. A020639.
Sequence in context: A004490 A135060 A191836 * A096123 A081125 A138570
Adjacent sequences: A072483 A072484 A072485 * A072487 A072488 A072489
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 13 2002
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EXTENSIONS
| More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 25 2003
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