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