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A071575 Number of iterations of cototient(n) needed to reach 1 (cototient(x) = x-phi(x)). 1
0, 1, 1, 2, 1, 3, 1, 3, 2, 4, 1, 4, 1, 4, 2, 4, 1, 5, 1, 5, 3, 5, 1, 5, 2, 5, 3, 5, 1, 6, 1, 5, 2, 6, 2, 6, 1, 6, 3, 6, 1, 7, 1, 6, 4, 6, 1, 6, 2, 7, 2, 6, 1, 7, 3, 6, 4, 7, 1, 7, 1, 6, 4, 6, 2, 7, 1, 7, 3, 7, 1, 7, 1, 7, 3, 7, 2, 8, 1, 7, 4, 8, 1, 8, 4, 7, 2, 7, 1, 8, 2, 7, 3, 7, 2, 7, 1, 7, 4, 8, 1, 8, 1, 7, 5, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Equals A076640(n)-1.

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

FORMULA

a(n) = a(n-phi(n))+1, a(1) = 0.

EXAMPLE

cototient(6) = 4 cototient(4) = 2 cototient(2) = 1 hence a(6) = 3

PROG

(PARI) for(n=1, 150, s=n; t=0; while(s!=1, t++; s=s-eulerphi(s); if(s==1, print1(t, ", "); ); ))

CROSSREFS

Cf. A032358.

Sequence in context: A029231 A025808 A144079 * A316436 A303674 A038569

Adjacent sequences:  A071572 A071573 A071574 * A071576 A071577 A071578

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, May 31 2002

EXTENSIONS

Prepended a(1)=0 and changed offset. - T. D. Noe, Dec 03 2008

STATUS

approved

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Last modified January 19 16:32 EST 2019. Contains 319309 sequences. (Running on oeis4.)