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A136183 a(n) = Sum_{k=1 to d(n)-1} LCM(b(k),b(k+1)), where b(k) is the k-th positive divisor of n and d(n) = number of positive divisors of n. 4
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; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = sum of the terms in row n of A136181.

LINKS

H. v. Eitzen, Table of n, a(n) for n=1..10000

Index entries for sequences related to lcm's

EXAMPLE

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.

MAPLE

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) ; # R. J. Mathar, Jul 20 2009

PROG

(PARI) A136183(n) = local(d=divisors(n)); vector(#d-1, x, lcm(d[x], d[x+1]))*vector(#d-1, x, 1)~

(Haskell)

a136183 n = sum $ zipWith lcm ps $ tail ps where ps = a027750_row n

-- Reinhard Zumkeller, Dec 20 2014

CROSSREFS

Cf. A136180, A136181, A136182.

Cf. A027750.

Sequence in context: A053570 A129647 A225652 * A100211 A071257 A067392

Adjacent sequences:  A136180 A136181 A136182 * A136184 A136185 A136186

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 19 2007

EXTENSIONS

Extended beyond a(12) by R. J. Mathar, Jul 20 2009

STATUS

approved

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Last modified December 2 19:13 EST 2016. Contains 278683 sequences.