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A063740 Number of k such that cototient(k) = n. 5
1, 1, 2, 1, 1, 2, 3, 2, 0, 2, 3, 2, 1, 2, 3, 3, 1, 3, 1, 3, 1, 4, 4, 3, 0, 4, 1, 4, 3, 3, 4, 3, 0, 5, 2, 2, 1, 4, 1, 5, 1, 4, 2, 4, 2, 6, 5, 5, 0, 3, 0, 6, 2, 4, 2, 5, 0, 7, 4, 3, 1, 8, 4, 6, 1, 3, 1, 5, 2, 7, 3, 5, 1, 7, 1, 8, 1, 5, 2, 6, 1, 9, 2, 6, 0, 4, 2, 10, 2, 4, 2, 5, 2, 7, 5, 4, 1, 8, 0, 9, 1, 6, 1, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,3

LINKS

T. D. Noe, Table of n, a(n) for n = 2..10000

EXAMPLE

Cototient(x) = 101 for x in {485,1157,1577,1817,2117,2201,2501,2537,10201}, with a(101)=8 terms; e.g. 485-Phi[485]=485-384=101. Cototient(x) = 102 only for x = 202 so a(102) = 1.

MATHEMATICA

Table[Count[Range[n^2], k_ /; k - EulerPhi@ k == n], {n, 2, 105}] (* Michael De Vlieger, Mar 17 2017 *)

PROG

(PARI) first(n)=my(v=vector(n), t); forcomposite(k=4, n^2, t=k-eulerphi(k); if(t<=n, v[t]++)); v[2..n] \\ Charles R Greathouse IV, Mar 17 2017

CROSSREFS

Cf. A000010, A051953, A063507.

Cf. A063748 (greatest solution to x-phi(x)=n)

Sequence in context: A133771 A217612 A029254 * A072782 A122563 A204030

Adjacent sequences:  A063737 A063738 A063739 * A063741 A063742 A063743

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 13 2001

EXTENSIONS

Name edited by Charles R Greathouse IV, Mar 17 2017

STATUS

approved

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Last modified April 27 04:48 EDT 2017. Contains 285507 sequences.