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A133422 Number of steps to reach 1 under repeated applications of the "7x+1" map of A133421, or -1 if 1 is never reached. 1
0, 1, 1, 2, 1, 2, 4, 3, 2, 2, 12, 3, 9, 5, 2, 4, 6, 3, 21, 3, 5, 13, 6, 4, 2, 10, 3, 6, 10, 3, 47, 5, 13, 7, 5, 4, 13, 22, 10, 4, 8, 6, 46, 14, 3, 7, 16, 5, 50, 3, 7, 11, 51, 4, 13, 7, 22, 11, 10, 4, 9, 48, 6, 6, 10, 14, 19, 8, 7, 6, 17, 5, 10, 14, 3, 23, 7, 11, 17, 5, 4, 9, 14, 7, 7, 47, 11, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
The 7x+1 map sends x to x/2 if x is even, x/3 if x is divisible by 3, x/5 if x is divisible by 5, otherwise 7x+1.
LINKS
Tomás Oliveira e Silva, The px+1 problem
MATHEMATICA
nxt[x_]:= Which[Mod[x, 2]==0, x/2, Mod[x, 3]==0, x/3, Mod[x, 5]==0, x/5, True, 7x+1]; Table[First[First[Position[NestList[nxt, i, 100], 1]]]-1, {i, 50}] - _Harvey P. Dale_, Dec 27 2007
CROSSREFS
Cf. A133421, A133419, ...
Sequence in context: A101897 A208058 A078142 * A331136 A099312 A117505
KEYWORD
nonn,easy
AUTHOR
_N. J. A. Sloane_, Nov 27 2007
EXTENSIONS
More terms from _Harvey P. Dale_, Dec 27 2007
More terms from _Sean A. Irvine_, Mar 29 2010
STATUS
approved

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Last modified March 5 03:04 EST 2024. Contains 370537 sequences. (Running on oeis4.)