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A176816 The number of steps to reach 0 under the map x -> x-tau(sigma(x)), starting at n. 1
1, 1, 1, 2, 2, 1, 2, 3, 3, 3, 3, 2, 4, 2, 3, 3, 4, 3, 5, 3, 4, 5, 4, 3, 5, 4, 6, 4, 5, 4, 6, 5, 5, 5, 6, 6, 6, 5, 7, 5, 6, 5, 7, 6, 7, 6, 7, 6, 8, 7, 8, 7, 8, 6, 8, 6, 8, 7, 8, 7, 9, 8, 9, 9, 9, 9, 10, 7, 9, 9, 9, 10, 10, 10, 10, 10, 10, 9, 10, 11, 10, 10, 10, 11, 11, 11, 10, 10, 11, 10, 11, 11, 12, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..94.

EXAMPLE

a(19)=5 because

f(19) = 19 - tau(sigma(19)) = 19 - tau(20) = 19 - 6 = 13;

f(13) = 13 - tau(sigma(13)) = 13 - tau(14) = 13 - 4 = 9;

f(9) = 9 - tau(sigma(9)) = 9 - tau(13) = 9 - 2 = 7;

f(7) = 7- tau(sigma(7)) = 7 - tau(8) = 7 - 4 = 3;

f(3) = 3- tau(sigma(3)) = 3 - tau(4) = 3 - 3 = 0;

MAPLE

A062068 := proc(n)

        numtheory[tau](numtheory[sigma](n)) ;

end proc:

A176816 := proc(n)

        a := 0 ;

        x := n ;

        while x <> 0 do

                x := x-A062068(x) ;

                a := a+1 ;

        end do:

        a ;

end proc: # R. J. Mathar, Oct 11 2011

CROSSREFS

Cf. A062068.

Sequence in context: A194258 A165927 A127830 * A053284 A050371 A172313

Adjacent sequences:  A176813 A176814 A176815 * A176817 A176818 A176819

KEYWORD

nonn

AUTHOR

Michel Lagneau, Apr 26 2010

STATUS

approved

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Last modified November 17 18:24 EST 2019. Contains 329241 sequences. (Running on oeis4.)