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Search: id:A136193
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| A136193 |
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Irregular array read by rows: row n contains the products of each pair of consecutive positive divisors of n. |
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2
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| 2, 3, 2, 8, 5, 2, 6, 18, 7, 2, 8, 32, 3, 27, 2, 10, 50, 11, 2, 6, 12, 24, 72, 13, 2, 14, 98, 3, 15, 75, 2, 8, 32, 128, 17, 2, 6, 18, 54, 162, 19, 2, 8, 20, 50, 200, 3, 21, 147, 2, 22, 242, 23, 2, 6, 12, 24, 48, 96, 288, 5, 125
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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The first listed row is row 2. Row n contains d(n)-1 terms, where d(n) is the number of positive divisors of n.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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The positive divisors of 20 are 1,2,4,5,10,20. 1*2=2. 2*4=8. 4*5=20. 5*10=50. 10*20=200. So row 20 is (2,8,20,50,200).
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MAPLE
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with(numtheory): a:=proc(n) local div: div:=divisors(n): seq(div[j]*div[j+1], j=1..tau(n)-1) end proc: for n from 2 to 25 do a(n) end do; # yields sequence as a two-dimensional array - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 08 2008
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CROSSREFS
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Cf. A078730, A136195, A136181.
Sequence in context: A063708 A096488 A011280 this_sequence A098513 A134347 A057761
Adjacent sequences: A136190 A136191 A136192 this_sequence A136194 A136195 A136196
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KEYWORD
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more,nonn,tabf
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AUTHOR
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Leroy Quet Dec 20 2007; corrected Jan 20 2008
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 08 2008
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