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A065152 Cototient(totient(n)) - totient(cototient(n)). 2
0, -1, 0, 0, 1, -1, 3, 0, 2, 0, 5, -2, 7, 0, -2, 0, 7, 0, 11, 0, 2, 2, 11, -4, 8, 2, 6, 0, 15, -6, 21, 0, 0, 2, 6, 0, 23, 4, 8, 0, 23, 0, 29, 4, 4, 4, 23, -8, 24, 4, -2, 4, 27, 0, 16, 0, 12, 8, 29, -12, 43, 6, 6, 0, 16, -10, 45, 4, 4, -6, 45, 0, 47, 6, 0, 8, 28, -2, 53, 0, 18, 12, 41, 0, 20, 10, 2, 8, 47, -4, 30, 8, 24, 8, 26, -16, 63, 6, 20, 8, 59, -8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000

FORMULA

a(n) = (phi(n) - phi(phi(n))) - (phi(n - phi(n))) = A000010(A051953(n)) - A051953(A000010(n)).

EXAMPLE

a(100) = 8, since phi(100) = 40, 100 - phi(100) = 60 = cototient(100), cototient(40) = 40 - 16 = 24, totient(60) = 16 so a(100) = 24 - 16 = 8.

MATHEMATICA

coTotient[n_] := n - EulerPhi@n; A065152[n_] := coTotient@ EulerPhi@ n - EulerPhi@ coTotient@ n; Array[A065152, 102] (* Robert G. Wilson v, Feb 24 2010 *)

PROG

(PARI) { for (n = 1, 1000, t=eulerphi(n); c=n - t; if (n>1, a=t - eulerphi(t) - eulerphi(c), a=0); write("b065152.txt", n, " ", a) ) } \\  Harry J. Smith, Oct 13 2009

CROSSREFS

Cf. A065153, A065154, A065155 (positions of zeros, negative, and positive numbers).

Sequence in context: A061064 A016597 A128114 * A171759 A073538 A022898

Adjacent sequences:  A065149 A065150 A065151 * A065153 A065154 A065155

KEYWORD

sign

AUTHOR

Labos Elemer, Oct 19 2001

STATUS

approved

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Last modified May 15 12:25 EDT 2021. Contains 343916 sequences. (Running on oeis4.)