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A070994 Numbers n such that the trajectory of n under the `3x+1' map reaches phi(n). 0
2, 3, 4, 5, 6, 8, 10, 11, 12, 15, 16, 17, 20, 22, 24, 25, 30, 32, 33, 34, 40, 41, 44, 47, 48, 50, 55, 59, 60, 64, 66, 71, 82, 85, 87, 88, 89, 94, 100, 107, 110, 118, 128, 132, 142, 164, 165, 170, 174, 178, 188, 214, 220, 235, 256, 328, 330, 340, 348, 376, 440, 470 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If n is a power of 2, n is in the sequence.

LINKS

Table of n, a(n) for n=1..62.

EXAMPLE

trajectory of 10 is : (10,5,16,8,4,2,1) and phi(10)=4 is reached, hence 10 is in the sequence.

PROG

(PARI) for(n=1, 10000, s=n; t=0; while(s!=1, t++; if(s%2==0, s=s/2, s=3*s+1); if(s==eulerphi(n), print1(n, ", "); ); ))

CROSSREFS

Sequence in context: A180636 A182625 A088232 * A291686 A057197 A067936

Adjacent sequences:  A070991 A070992 A070993 * A070995 A070996 A070997

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, May 18 2002

STATUS

approved

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Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)