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A136131
Values of n such that (sigma(sigma(n))-phi(phi(n)))/n is an integer (the corresponding integral ratios are given in A136132).
3
1, 3, 5, 18, 32, 36, 92, 144, 368, 576, 712, 800, 888, 918, 928, 1472, 3193, 4600, 4768, 8800, 9288, 10602, 13032, 16172, 21204, 26856, 36864, 56832, 61792, 84816, 93176, 94208, 96768, 160416, 229888, 339264, 441440, 589824, 670746, 746334, 834048, 893268
OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..92 (terms < 10^10)
EXAMPLE
n = 92 is in the sequence because sigma(sigma(92))-phi(phi(92)) = sigma(168)-phi(44) = 480-20 = 460 = 5*92.
MAPLE
with(numtheory): a:=proc(n) if type((sigma(sigma(n))-phi(phi(n)))/n, integer) =true then n else end if end proc: seq(a(n), n=1..100000);
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Mar 03 2008
STATUS
approved