A266269 a(n) is the smallest number k such that phi(k) >= n*phi(k-1).

2, 3, 7, 211, 30031, 223092871, 13082761331670031, 3217644767340672907899084554131

Offset

1,1

Links

Table of n, a(n) for n=1..8.

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

Cf. A000010 (phi), A266276 (the smallest k such that phi(k) = n*phi(k-1)).

Sequence in context: A053924 A130060 A224894 * A053942 A053954 A063869

Adjacent sequences: A266266 A266267 A266268 * A266270 A266271 A266272

Keyword

nonn,more

Author

Jaroslav Krizek, Jan 26 2016

Extensions

a(6)-a(8) from Jinyuan Wang, Nov 01 2020

Status

approved