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Search: id:A115958
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| A115958 |
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Numbers n having exactly 4 distinct prime factors, the largest of which is greater than or equal to sqrt(n) (i.e. sqrt(n)-rough numbers with exactly 4 distinct prime factors). |
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+0
6
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| 930, 1110, 1230, 1290, 1410, 1590, 1770, 1806, 1830, 1974, 2010, 2130, 2190, 2226, 2370, 2478, 2490, 2562, 2670, 2814, 2910, 2982, 3030, 3066, 3090, 3210, 3270, 3318, 3390, 3486, 3660, 3738, 3810, 3930, 4020, 4074, 4110, 4170, 4242, 4260, 4326, 4380
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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3660 is in the sequence because it has 4 distinct prime factors
(2, 3, 5, and 61) and 61>sqrt(3660).
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MAPLE
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with(numtheory): a:=proc(n) if nops(factorset(n))=4 and factorset(n)[4]^2>=n then n else fi end: seq(a(n), n=1..4500);
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CROSSREFS
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Cf. A115956, A115957, A115959, A115960, A115961.
Sequence in context: A074889 A109184 A068651 this_sequence A035856 A093231 A105213
Adjacent sequences: A115955 A115956 A115957 this_sequence A115959 A115960 A115961
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 02 2006
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