A090556 Beginning with 1, a(n) = least number m > a(n-1) such that phi(a(n-1)) divides phi(m).

1, 2, 3, 4, 5, 8, 10, 12, 13, 21, 26, 28, 35, 39, 45, 52, 56, 65, 97, 119, 153, 193, 221, 291, 357, 386, 388, 416, 442, 448, 476, 485, 579, 595, 663, 765, 769, 965, 1105, 1455, 1538, 1544, 1552, 1649, 1799, 2307, 2313, 2895, 3076, 3088, 3104, 3281, 3341, 3845, 4947

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..308

Formula

a(1)=1, then a(n+1) = A069797(a(n)). - Ivan Neretin, May 01 2016

Mathematica

NestList[Function[n, SelectFirst[Range[n + 1, 10^4], Divisible[EulerPhi@ #, EulerPhi@ n] &]], 1, 54] (* Michael De Vlieger, May 01 2016, Version 10 *)

Crossrefs

Cf. A014573, A090557.

Sequence in context: A005233 A155736 A074897 * A369152 A223539 A332520

Adjacent sequences: A090553 A090554 A090555 * A090557 A090558 A090559

Keyword

nonn

Author

Amarnath Murthy, Dec 10 2003

Extensions

Corrected and extended by Sam Handler (sam_5_5_5_0(AT)yahoo.com), Nov 03 2004

Status

approved