OFFSET
1,1
EXAMPLE
a(3) = 7 because 7 is the smallest number k such that phi(k) >= n*phi(k-1); phi(7) = 6 >= 3*phi(6) = 3*2.
PROG
(Magma) a:=func<n | exists(r){k:k in[2..10^7] | Floor(EulerPhi(k) / EulerPhi(k-1)) eq n}select r else 0>; [a(n):n in[1..5]]
(PARI) a(n) = {my(k=2, e=1); while(n*e > e=eulerphi(k), k++); k; } \\ Jinyuan Wang, Nov 01 2020
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jaroslav Krizek, Jan 26 2016
EXTENSIONS
a(6)-a(8) from Jinyuan Wang, Nov 01 2020
STATUS
approved