A378640 Smallest m such that phi(m) does not divide n, where phi is the Euler totient function (A000010).

3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 15, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5, 3, 7, 3, 5, 3, 7, 3, 5, 3, 11, 3, 5

Offset

1,1

Comments

Up to n = 10^7 the distinct terms of the sequence (which are also the record values) are {3, 5, 7, 11, 15, 17, 19, 23, 29, 47, 51, 53}. Is this A076245 (for n >= 2)?

First differs from A095366 at n = 60.

It appears that a(n) = A095366(n) except when n = 60*(2*k + 1), with k >= 0, where a(n) = 15 while A095366(n) = 17.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Formula

a(n) = 3 if n is odd.

Mathematica

A378640[n_] := If[OddQ[n], 3, Module[{m = 4}, While[Divisible[n, EulerPhi[++m]]]; m]];
Array[A378640, 100]

Crossrefs

Cf. A000010, A076245, A095366, A378638, A378641, A378642.

Sequence in context: A118271 A260689 A328386 * A095366 A029604 A079602

Adjacent sequences: A378637 A378638 A378639 * A378641 A378642 A378643

Keyword

nonn,easy

Author

Paolo Xausa, Dec 05 2024

Status

approved