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A008882
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3x+1 sequence starting at 99.
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4
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99, 298, 149, 448, 224, 112, 56, 28, 14, 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4
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listen;
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internal format)
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OFFSET
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0,1
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, E16.
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LINKS
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MAPLE
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f := proc(n) option remember; if n = 0 then 99; 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]&, 99, 70] (* Harvey P. Dale, Jul 28 2014 *)
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PROG
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(Magma) [n eq 1 select 99 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..80]]; // Vincenzo Librandi, Jul 29 2014
(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(99, 60)) \\ A008882 (from 99 first 60)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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