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A061799
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Smallest number with at least n divisors.
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11
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1, 2, 4, 6, 12, 12, 24, 24, 36, 48, 60, 60, 120, 120, 120, 120, 180, 180, 240, 240, 360, 360, 360, 360, 720, 720, 720, 720, 720, 720, 840, 840, 1260, 1260, 1260, 1260, 1680, 1680, 1680, 1680, 2520, 2520, 2520, 2520, 2520, 2520, 2520, 2520, 5040, 5040, 5040
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Smallest number which can be expressed as the least common multiple of n distinct numbers. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 27 2002
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..2000 (using A002182)
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EXAMPLE
| a(5)=12 since every number less than 12 has fewer than five divisors
(1 has one; 2,3,5,7 and 11 have two each; 4 and 9 have three each;
6,8 and 10 have four each) while 12 has at least five
(in fact it has six: 1,2,3,4,6 and 12).
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MATHEMATICA
| Reap[ For[ n = 1, n <= 100, n++, s = n; While[ DivisorSigma[0, s] < n, s++]; Sow[s] ] ][[2, 1]] (* From Jean-François Alcover, Feb 16 2012, after Pari *)
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PROG
| (PARI) for(n=1, 100, s=n; while(numdiv(s)<n, s++); print1(s, ", "))
(Haskell)
import Data.List (findIndex)
import Data.Maybe (fromJust)
a061799 n = succ $ fromJust $ findIndex (n <=) $ map a000005 [1..]
-- Reinhard Zumkeller, Apr 01 2011
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CROSSREFS
| Cf. A000005, A002182, A002183, A005179.
Sequence in context: A053146 A056675 A062857 * A076868 A056793 A137387
Adjacent sequences: A061796 A061797 A061798 * A061800 A061801 A061802
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KEYWORD
| nice,nonn,changed
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AUTHOR
| Henry Bottomley (se16(AT)btinternet.com), Jun 22 2001
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EXTENSIONS
| Replaced "factors" by "divisors" in definition and example M. F. Hasler (MHasler(AT)univ-ag.fr), Oct 24 2010
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