OFFSET
1,1
COMMENTS
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..46 (terms < 10^13)
EXAMPLE
17 is a term because sigma(16) - phi(16) = 31-8 = 23 = (3*17-5)/2.
MATHEMATICA
Select[Range[10^6], 2 (DivisorSigma[1, # - 1] - EulerPhi[# - 1]) == 3 # - 5 &] (* Michael De Vlieger, Mar 24 2016 *)
PROG
(Magma) [n: n in[1..10^7] | 2*(SumOfDivisors(n-1) - EulerPhi(n-1)) eq 3*n-5]
(PARI) lista(nn) = {for(n=2, nn, if(sigma(n-1) - eulerphi(n-1) == (3*n-5)/2, print1(n, ", "))); } \\ Altug Alkan, Mar 23 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Mar 23 2016
EXTENSIONS
a(30)-a(32) from Michel Marcus, Apr 05 2016
a(33)-a(35) from Giovanni Resta, Apr 11 2016
STATUS
approved