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A007547
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Number of steps to compute n-th prime in PRIMEGAME (slow version).
(Formerly M5075)
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7
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19, 69, 281, 710, 2375, 3893, 8102, 11361, 19268, 36981, 45680, 75417, 101354, 118093, 152344, 215797, 293897, 327571, 429229, 508284, 556494, 701008, 809381, 990746, 1274952, 1435957, 1531854, 1712701, 1820085, 2021938, 2835628, 3107393, 3549288, 3723821
(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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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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Table of n, a(n) for n=1..34.
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.
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MAPLE
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a:= proc(n) option remember; local l, p, m, k;
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, 55/1]:
if n=1 then b(0):= 2; a(0):= 0 else a(n-1) fi;
p:= b(n-1);
for m do for k while not type(p*l[k], integer) do od;
p:= p*l[k];
if 2^ilog2(p)=p then break fi
od:
b(n):= p;
m + a(n-1)
end:
seq(a(n), n=1..10); # Alois P. Heinz, May 01 2011
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MATHEMATICA
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Clear[a]; a[n_] := a[n] = Module[{l, p, m, k}, 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, 55/1}; If[n == 1, b[0] = 2; a[0] = 0, a[n-1]]; p = b[n-1]; For[m=1, True, m++, For[k=1, !IntegerQ[p*l[[k]]], k++]; p = p*l[[k]]; If[2^(Length[IntegerDigits[p, 2]]-1) == p, Break[]]]; b[n] = p; m + a[n-1]]; Table[Print[a[n]]; a[n], {n, 1, 30}] (* Jean-François Alcover, Nov 25 2014, after Alois P. Heinz *)
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PROG
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(Haskell)
import Data.List (elemIndices)
a007547 n = a007547_list !! n
a007547_list = tail $ elemIndices 2 $ map a006530 a007542_list
-- Reinhard Zumkeller, Jan 24 2012
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CROSSREFS
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Cf. A007542, A007546.
Cf. A006530, A034785.
Sequence in context: A300463 A204675 A007546 * A217081 A010007 A172078
Adjacent sequences: A007544 A007545 A007546 * A007548 A007549 A007550
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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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EXTENSIONS
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More terms from Alois P. Heinz, May 01 2011
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STATUS
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approved
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