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Search: id:A136183
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| A136183 |
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a(n) = Sum_{k=1 to d(n)-1} LCM(b(k),b(k+1)), where b(k) is the kth positive divisor of n and d(n) = number of positive divisors of n. |
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4
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| 0, 2, 3, 6, 5, 14, 7, 14, 12, 22, 11, 44, 13, 30, 33, 30, 17, 50, 19, 56, 45, 46, 23, 104, 30, 54, 39, 76, 29, 143, 31, 62, 69, 70, 75, 158, 37, 78, 81, 166, 41, 154, 43, 116, 153, 94, 47, 224, 56, 122, 105, 136, 53, 158, 115, 230, 117, 118, 59, 400, 61, 126, 213, 126, 135
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) = sum of the terms in row n of A136181.
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LINKS
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H. v. EItzen, Table of n, a(n) for n=1..10000
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. LCM(1,2)=2. LCM(2,4)=4. LCM(4,5)=20. LCM(5,10)=10. And LCM(10,20)=20. So a(20) = 2+4+20+10+20 = 56.
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MAPLE
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A136181row := proc(n) local dvs; dvs := sort(convert(numtheory[divisors](n), list)) ; seq(lcm(op(d-1, dvs), op(d, dvs)), d=2..nops(dvs)) ; end: A136183 := proc(n) if n = 1 then 0; else add(l, l= A136181row(n) ) ; fi; end: seq(A136183 (n), n=1..70) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009]
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PROGRAM
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(PARI) A136183(n) = local(d=divisors(n)); vector(#d-1, x, lcm(d[x], d[x+1]))*vector(#d-1, x, 1)~
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CROSSREFS
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Cf. A136180, A136181, A136182.
Adjacent sequences: A136180 A136181 A136182 this_sequence A136184 A136185 A136186
Sequence in context: A002517 A053570 A129647 this_sequence A100211 A071257 A067392
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Dec 19 2007
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EXTENSIONS
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Extended beyond a(12) by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 20 2009
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