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A008884
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3x+1 sequence starting at 27.
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12
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27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, 322, 161, 484, 242, 121, 364, 182, 91, 274, 137, 412, 206, 103, 310, 155, 466, 233, 700, 350, 175, 526, 263, 790, 395, 1186, 593, 1780, 890, 445, 1336, 668, 334, 167, 502, 251, 754, 377, 1132, 566, 283, 850, 425, 1276, 638, 319, 958, 479, 1438, 719, 2158, 1079
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,1
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COMMENTS
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At step 109 enters the loop 4 2 1 4 2 1 4 2 1 ... - N. J. A. Sloane, Jul 27 2019
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, E16.
H.-O. Peitgen et al., Chaos and Fractals, Springer, p. 33.
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LINKS
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F. Oort, Prime numbers, 2013, ICCM Notices, Talk at Academia Sinica and National Taiwan University, 17-XII-2012.
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FORMULA
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MAPLE
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f := proc(n) option remember; if n = 0 then 27; elif f(n-1) mod 2 = 0 then f(n-1)/2 else 3*f(n-1)+1; fi; end;
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MATHEMATICA
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NestList[If[EvenQ[#], #/2, 3#+1]&, 27, 70] (* Harvey P. Dale, Jun 30 2011 *)
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PROG
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(Magma) [ n eq 1 select 27 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..70] ]; // Klaus Brockhaus, Dec 25 2010
(PARI) Collatz(n, lim=0)={
my(c=n, e=0, L=List(n)); if(lim==0, e=1; lim=n*10^6);
for(i=1, lim, if(c%2==0, c=c/2, c=3*c+1); listput(L, c); if(e&&c==1, break));
return(Vec(L)); }
print(Collatz(27)) \\ A008884 (from 27 to the first 1)
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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EXTENSIONS
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More terms from Larry Reeves (larryr(AT)acm.org), Apr 27 2001
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STATUS
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approved
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