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Search: id:A014613
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| A014613 |
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Numbers that are products of 4 primes (or 4-almost primes, a generalization of semiprimes). |
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+0
99
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| 16, 24, 36, 40, 54, 56, 60, 81, 84, 88, 90, 100, 104, 126, 132, 135, 136, 140, 150, 152, 156, 184, 189, 196, 198, 204, 210, 220, 225, 228, 232, 234, 248, 250, 260, 276, 294, 296, 297, 306, 308, 315, 328, 330, 340, 342, 344, 348, 350, 351, 364, 372, 375, 376
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Also called "quadruprimes". Divisible by exactly 4 primes (counted with multiplicity).
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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FORMULA
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Product p_i^e_i with Sum e_i = 4.
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MATHEMATICA
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Select[Range[200], Plus @@ Last /@ FactorInteger[ # ] == 4 &] - Vladimir Orlovsky, Apr 23 2008
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CROSSREFS
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Cf. A000040, A001358, A014614, A033987, A114106 (number of 4-almost primes <= 10^n).
Sequence in context: A036328 A067028 A110893 this_sequence A046370 A103248 A140135
Adjacent sequences: A014610 A014611 A014612 this_sequence A014614 A014615 A014616
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KEYWORD
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nonn
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AUTHOR
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Eric Weisstein (eric(AT)weisstein.com)
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EXTENSIONS
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More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), Jun 15 1998.
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