OFFSET
1,2
COMMENTS
a(n) = sum of the terms in row n of A136181.
LINKS
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
MATHEMATICA
Table[Total@ Apply[LCM, Partition[Divisors@ n, 2, 1], 1], {n, 65}] (* Michael De Vlieger, Sep 21 2017 *)
PROG
(PARI) A136183(n) = local(d=divisors(n)); vector(#d-1, x, lcm(d[x], d[x+1]))*vector(#d-1, x, 1)~
(PARI) a(n) = my(d=divisors(n)); vecsum(vector(#d-1, k, lcm(d[k], d[k+1]))); \\ Michel Marcus, Sep 22 2017
(Haskell)
a136183 n = sum $ zipWith lcm ps $ tail ps where ps = a027750_row n
-- Reinhard Zumkeller, Dec 20 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 19 2007
EXTENSIONS
Extended beyond a(12) by R. J. Mathar, Jul 20 2009
STATUS
approved