A066659 Least k > n such that phi(k) = phi(n), if such k exists; = 0 otherwise.

2, 0, 4, 6, 8, 0, 9, 10, 14, 12, 22, 0, 21, 18, 16, 20, 32, 0, 27, 24, 26, 0, 46, 30, 33, 28, 38, 36, 58, 0, 62, 34, 44, 40, 39, 42, 57, 54, 45, 48, 55, 0, 49, 50, 52, 0, 94, 60, 86, 66, 64, 56, 106, 0, 75, 70, 63, 0, 118, 0, 77, 0, 74, 68, 104, 0, 134, 80, 92, 72, 142, 78, 91

Offset

1,1

Links

Paul Tek, Table of n, a(n) for n = 1..10000

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Mathematica

Table[k = n + 1; While[And[k <= 2 n + 1, EulerPhi@ k != EulerPhi@ n], k++]; Boole[k < 2 n + 1] k, {n, 73}] (* Michael De Vlieger, Dec 31 2016 *)

Prog

(PARI) a(n) = {my(v = select(x -> x>n, invphi(eulerphi(n)))); if(#v == 0, 0, vecmin(v)); } \\ Amiram Eldar, Nov 14 2024, using Max Alekseyev's invphi.gp

Crossrefs

Cf. A000010, A043343.

Sequence in context: A322402 A196877 A098123 * A343468 A287846 A378131

Adjacent sequences: A066656 A066657 A066658 * A066660 A066661 A066662

Keyword

nonn

Author

Joseph L. Pe, Jan 10 2002

Extensions

More terms from Vladeta Jovovic, Jan 12 2002

Typo in data fixed by Paul Tek, Sep 20 2015

Status

approved