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A007542
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Successive integers produced by Conway's PRIMEGAME.
(Formerly M2084)
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10
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2, 15, 825, 725, 1925, 2275, 425, 390, 330, 290, 770, 910, 170, 156, 132, 116, 308, 364, 68, 4, 30, 225, 12375, 10875, 28875, 25375, 67375, 79625, 14875, 13650, 2550, 2340, 1980, 1740, 4620, 4060, 10780, 12740, 2380, 2184, 408, 152
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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REFERENCES
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J. H. Conway, FRACTRAN: a simple universal programming language for arithmetic, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 4-26.
R. K. Guy, Conway's prime producing machine. Math. Mag. 56 (1983), no. 1, 26-33.
D. Olivastro, Ancient Puzzles. Bantam Books, NY, 1993, p. 21.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Alois P. Heinz, Table of n, a(n) for n=1..8103
Eric Weisstein's World of Mathematics, FRACTRAN
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FORMULA
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a(n+1) = A203907(a(n)), a(1) = 2. [Reinhard Zumkeller, Jan 24 2012]
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MAPLE
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l:= [17/91, 78/85, 19/51, 23/38, 29/33, 77/29, 95/23, 77/19, 1/17, 11/13, 13/11, 15/2, 1/7, 55]: a:= proc(n) option remember; global l; local p, k; if n=1 then 2 else p:= a(n-1); for k while not type (p*l[k], integer) do od; p*l[k] fi end: seq (a(n), n=1..50); # Alois P. Heinz, Aug 12 2009
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MATHEMATICA
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lst := {17/91, 78/85, 19/51, 23/38, 29/33, 77/29, 95/23, 77/19, 1/17, 11/13, 13/11, 15/2, 1/7, 55}; a[1] = 2; a[n_] := a[n] = (p = a[n - 1]; k = 1; While[ ! IntegerQ[ p*lst[[k]]], k++]; p*lst[[k]]); Table[ a[n], {n, 1, 42}] (* From Jean-François Alcover, Jan 23 2012, after Alois P. Heinz *)
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PROG
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(Haskell)
a007542 n = a007542_list !! (n-1)
a007542_list = iterate a203907 2 -- Reinhard Zumkeller, Jan 24 2012
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CROSSREFS
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Cf. A007546, A007547, A183132.
Sequence in context: A012993 A216331 A179432 * A090604 A007467 A132317
Adjacent sequences: A007539 A007540 A007541 * A007543 A007544 A007545
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KEYWORD
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easy,nonn,nice
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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