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A211384 a(1) = 1, a(2) = 3; for n>2, a(n) = smallest number > a(n-1) such that a(n) is divisible by a(d) for all divisors d of n. 5
1, 3, 4, 6, 7, 12, 13, 18, 20, 21, 22, 24, 25, 39, 56, 72, 73, 120, 121, 126, 156, 198, 199, 216, 217, 225, 240, 312, 313, 336, 337, 360, 396, 438, 455, 480, 481, 726, 800, 882, 883, 936, 937, 990, 1120, 1194, 1195, 1296, 1300, 1302, 1460, 1800, 1801, 1920 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

EXAMPLE

a(6) = 12 is divisible by a(1) = 1, a(2) = 3, a(3) = 4.

MAPLE

a:= proc(n) a(n):= `if`(n<3, 2*n-1, (h-> ceil((a(n-1)+1)/h)*h)

    (ilcm(map(a, numtheory[divisors](n) minus {1, n})[]))) end:

seq(a(n), n=1..100);  # Alois P. Heinz, Feb 07 2013

MATHEMATICA

a[1] = 1; a[2] = 3; a[n_] := a[n] = (Ceiling[(a[n-1]+1)/#]*#&)[LCM @@ Map[a, Most[Divisors[n]]]]; Table[a[n], {n, 1, 60}] (* Jean-Fran├žois Alcover, Mar 27 2017, after Alois P. Heinz *)

CROSSREFS

Cf. A222208, A222209.

Sequence in context: A153883 A033162 A105133 * A281828 A002982 A290432

Adjacent sequences:  A211381 A211382 A211383 * A211385 A211386 A211387

KEYWORD

nonn

AUTHOR

J. Lowell, Feb 07 2013

EXTENSIONS

More terms from Alois P. Heinz, Feb 07 2013

STATUS

approved

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Last modified February 20 22:51 EST 2019. Contains 320362 sequences. (Running on oeis4.)