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A093432 a(n) = lcm_{k=1..n} (lcm(n,n-1,...,n-k+2,n-k+1)/lcm(1,2,...,k)). 3
1, 2, 3, 12, 10, 30, 105, 280, 252, 1260, 2310, 4620, 4290, 6006, 15015, 240240, 680680, 6126120, 11639628, 2771340, 1763580, 19399380, 223092870, 178474296, 171609900, 743642900, 1434168450, 20078358300, 19409079690, 19409079690, 300840735195, 875173047840 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..2363

EXAMPLE

a(4) = lcm(lcm(4)/lcm(1), lcm(4,3)/lcm(1,2), lcm(4,3,2)/lcm(1,2,3), lcm(4,3,2,1)/lcm(1,2,3,4)) = lcm(4,6,2,1) = 12.

MAPLE

T:=(n, k)->lcm(seq(i, i=n-k+1..n))/lcm(seq(j, j=1..k)): seq(lcm(seq(T(n, k), k=1..n)), n=1..35); # Emeric Deutsch, Jan 30 2006

# second Maple program:

b:= proc(n) option remember; `if`(n=1, 1, ilcm(b(n-1), n)) end:

a:= proc(n) option remember; local k, r, s; r, s:= 1, 1;

      for k to n do s:= ilcm(s, n-k+1); r:= ilcm(r, s/b(k)) od; r

    end:

seq(a(n), n=1..40);  # Alois P. Heinz, Mar 17 2018

MATHEMATICA

b[n_] := b[n] = If[n == 1, 1, LCM[b[n - 1], n]];

a[n_] := a[n] = Module[{k, r = 1, s = 1}, For[k = 1, k <= n, k++, s = LCM[s, n - k + 1]; r = LCM[r, s/b[k]]]; r];

Array[a, 40] (* Jean-Fran├žois Alcover, Jun 18 2018, after Alois P. Heinz *)

CROSSREFS

Cf. A093430, A093431, A093433.

LCM of the terms in row n of the triangle in A093430.

Sequence in context: A303221 A168059 A068550 * A212303 A100561 A081529

Adjacent sequences:  A093429 A093430 A093431 * A093433 A093434 A093435

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 December 8 08:49 EST 2019. Contains 329862 sequences. (Running on oeis4.)