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A109895 Group the natural numbers so that every 2n-th group product is divisible by the single number in the next group. (1), (2,3,4,5), (6), (7,8,9,10,11), (12), (13,14,15,16,17,18,19),(20), (21,22,23,24,25,26,27),(28),... Sequence contains the single members of the odd numbered groups. 3
1, 6, 12, 20, 28, 36, 45, 56, 70, 80, 90, 104, 112, 120, 132, 140, 154, 168, 180, 192, 208, 220, 234, 250, 264, 280, 297, 312, 324, 336, 350, 360, 378, 396, 416, 432, 448, 462, 480, 495, 504, 520, 539, 560, 576, 594, 612, 630, 640, 660, 672, 693, 714, 728, 748 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) divides (a(n)-1)! / (a(n-1)!) and is the smallest integer with this property. - Simon Nickerson (simonn(AT)maths.bham.ac.uk), Jul 15 2005

Essentially a duplicate of A079760. [From R. J. Mathar, Aug 18 2008]

LINKS

Table of n, a(n) for n=1..55.

PROG

(GAP) A := [ 1 ]; n := 1; repeat p := 1; k := n + 1; repeat p := p * k; k := k+1; until p mod k = 0; n := k; Add(A, n); until n > 10000; (Nickerson)

CROSSREFS

Cf. A079759, A109896, A109897.

Sequence in context: A286927 A189793 A079760 * A083209 A080714 A116368

Adjacent sequences:  A109892 A109893 A109894 * A109896 A109897 A109898

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Jul 13 2005

EXTENSIONS

More terms from Simon Nickerson (simonn(AT)maths.bham.ac.uk), Jul 15 2005

STATUS

approved

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Last modified May 27 21:52 EDT 2020. Contains 334671 sequences. (Running on oeis4.)