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A116998
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Numbers having no fewer distinct prime factors than any predecessor; a(1) = 1.
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5
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1, 2, 3, 4, 5, 6, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 28, 30, 42, 60, 66, 70, 78, 84, 90, 102, 105, 110, 114, 120, 126, 130, 132, 138, 140, 150, 154, 156, 165, 168, 170, 174, 180, 182, 186, 190, 195, 198, 204, 210, 330, 390, 420, 462, 510, 546, 570, 630, 660
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OFFSET
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1,2
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COMMENTS
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The unitary version of Ramanujan's largely composite numbers (A067128), numbers having no fewer unitary divisors than any predecessor. - Amiram Eldar, Jun 08 2019
Called omega-largely composite numbers by Erdős and Nicolas (1981). - Amiram Eldar, Jun 24 2023
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LINKS
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MAPLE
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a:= proc(n) option remember; local k, t;
t:= nops(ifactors(a(n-1))[2]);
for k from 1+a(n-1) while nops(ifactors(k)[2])<t do od; k
end: a(1):=1:
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MATHEMATICA
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a[1] = 1; a[n_] := a[n] = For[nu = PrimeNu[a[n-1]]; k = a[n-1]+1, True, k++, If[PrimeNu[k] >= nu, Return[k]]]; Array[a, 80] (* Jean-François Alcover, Apr 11 2017 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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