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A007542 Successive integers produced by Conway's PRIMEGAME.
(Formerly M2084)
10
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)
OFFSET

1,1

REFERENCES

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).

LINKS

Alois P. Heinz, Table of n, a(n) for n=1..8103

Eric Weisstein's World of Mathematics, FRACTRAN

FORMULA

a(n+1) = A203907(a(n)), a(1) = 2. [Reinhard Zumkeller, Jan 24 2012]

MAPLE

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

MATHEMATICA

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}] (* Jean-Fran├žois Alcover, Jan 23 2012, after Alois P. Heinz *)

PROG

(Haskell)

a007542 n = a007542_list !! (n-1)

a007542_list = iterate a203907 2  -- Reinhard Zumkeller, Jan 24 2012

CROSSREFS

Cf. A007546, A007547, A183132.

Sequence in context: A012993 A216331 A179432 * A090604 A007467 A132317

Adjacent sequences:  A007539 A007540 A007541 * A007543 A007544 A007545

KEYWORD

easy,nonn,look,nice

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 28 00:22 EST 2014. Contains 250286 sequences.