A087258 a(n) = gcd(n, A025586(n)), greatest common divisor of n and largest value in 3x+1 iteration list started at n.

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

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: A356166 A327405 A322362 * A333763 A076775 A357689

Adjacent sequences: A087255 A087256 A087257 * A087259 A087260 A087261

Keyword

nonn

Author

Labos Elemer, Sep 09 2003

Status

approved