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A067226
Numbers k such that phi(5k+1) = sigma(k).
2
5005, 6745, 79695, 99145, 160195, 166135, 296065, 350935, 486805, 960355, 1291105, 1350745, 1817365, 2218645, 2445685, 3287680, 4069135, 5341375, 5497965, 8933085, 14495065, 15106795, 16824535, 16850995, 18510055, 18710125, 21309085, 21521500, 22453345
OFFSET
1,1
COMMENTS
Are there any terms not congruent to 5 in the sequence?
a(58) = 104447959 is the first example. - Charles R Greathouse IV, Jan 29 2012
MATHEMATICA
Select[Range[10^6], EulerPhi[5*# + 1] == DivisorSigma[1, #] &] (* Amiram Eldar, May 09 2022 *)
PROG
(PARI) for(n=1, 1e9, if(sigma(n)==eulerphi(5*n+1), print1(n", "))) \\ Charles R Greathouse IV, Jan 29 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 20 2002
EXTENSIONS
a(11)-a(29) from Donovan Johnson, Jan 29 2012
STATUS
approved