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A248817 Numbers that are equal to the arithmetic derivative of their cototient. 1
12, 32, 44, 332, 5103, 10935, 12555, 59049, 69255, 94041, 185895, 1114641, 1265625, 1453125, 3639916, 8015625, 10475212, 10521657, 12254625, 21515625, 146484375, 155649627, 178598385, 244603436, 362087739, 1408107267, 1540368225, 2186172700, 2490234375 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Solutions of the equation n = (n - phi(n))’.
a(32) > 10^11. - Hiroaki Yamanouchi, Sep 11 2015
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 1..31
EXAMPLE
Cototient of 12 is 12 - phi(12) = 12 - 4 = 8 and the arithmetic derivative of 8 is 12.
MAPLE
with(numtheory); P:= proc(q) local a, n, p; for n from 1 to q do
a:=(n-phi(n))*add(op(2, p)/op(1, p), p=ifactors(n-phi(n))[2]);
if n=a then print(n); fi; od; end: P(10^6);
CROSSREFS
Sequence in context: A242371 A118785 A071336 * A051519 A305074 A166959
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Oct 15 2014
EXTENSIONS
a(21)-a(29) from Hiroaki Yamanouchi, Sep 11 2015
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)