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A087258 a(n) = gcd(n, A025586(n)), greatest common divisor of n and largest value in 3x+1 iteration list started at n. 1
1, 2, 1, 4, 1, 2, 1, 8, 1, 2, 1, 4, 1, 2, 5, 16, 1, 2, 1, 20, 1, 2, 1, 24, 1, 2, 1, 4, 1, 10, 1, 32, 1, 2, 5, 4, 1, 2, 1, 40, 1, 2, 1, 4, 1, 2, 1, 48, 1, 2, 1, 52, 1, 2, 1, 56, 1, 2, 1, 20, 1, 2, 1, 64, 1, 2, 1, 68, 1, 10, 1, 72, 1, 2, 5, 4, 1, 2, 1, 80, 1, 2, 1, 84, 1, 2, 1, 88, 1, 2, 1, 4, 1, 2, 1, 96, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

Antti Karttunen, Data supplement: n, a(n) computed for n = 1..100000

Index entries for sequences related to 3x+1 (or Collatz) problem

MATHEMATICA

c[x_] := (1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1)c[1]=1; fpl[x_] := Delete[FixedPointList[c, x], -1] Table[GCD[w, Max[fpl[w]]], {w, 1, 256}]

PROG

(PARI)

A025586(n) = { my(r=n); while(n>2, if(n%2, n=3*n+1; if(n>r, r=n), n/=2)); (r); }; \\ From A025586

A087258(n) = gcd(n, A025586(n)); \\ Antti Karttunen, Dec 05 2018

CROSSREFS

Cf. A006370, A025586, A033496, A087259, A087260, A087262.

Sequence in context: A006519 A327405 A322362 * A333763 A076775 A324873

Adjacent sequences:  A087255 A087256 A087257 * A087259 A087260 A087261

KEYWORD

nonn

AUTHOR

Labos Elemer, Sep 09 2003

STATUS

approved

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Last modified April 20 06:59 EDT 2021. Contains 343125 sequences. (Running on oeis4.)