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A093431 a(n) = Sum_{k=1..n} (LCM(n,n-1,...,n-k+2,n-k+1)/LCM(1,2,...,k)). 13
1, 3, 7, 13, 31, 38, 113, 165, 265, 420, 1607, 1004, 3979, 6893, 4205, 8665, 40903, 49558, 315477, 162320, 79179, 269877, 1647123, 937552, 1810091, 8445653, 7791355, 3978237, 33071543, 19578860, 283536169, 327438713, 117635955 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The following sequences all appear to have the same parity: A003071, A029886, A061297, A092524, A093431, A102393, A104258, A122248, A128975. - Jeremy Gardiner, Dec 28 2008

LINKS

Table of n, a(n) for n=1..33.

MAPLE

a:= n-> add(ilcm(seq(i, i=n-k+1..n))/ilcm(seq(j, j=1..k)), k=1..n): seq(a(n), n=1..40); #  Emeric Deutsch, Jan 30 2006

MATHEMATICA

Table[Sum[(LCM@@(n-Range[0, k-1])/LCM@@Range[k]), {k, n}], {n, 33}] (* Jayanta Basu, May 22 2013 *)

CROSSREFS

Cf. A093430, A093432, A093433.

Row sums of A093430.

Sequence in context: A100750 A105435 A117708 * A243765 A256148 A083520

Adjacent sequences:  A093428 A093429 A093430 * A093432 A093433 A093434

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Mar 31 2004

EXTENSIONS

Corrected and extended by Emeric Deutsch, Jan 30 2006

STATUS

approved

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Last modified November 20 12:30 EST 2017. Contains 294971 sequences.