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A090556 Beginning with 1, a(n) = least number m > a(n-1) such that phi(a(n-1)) divides phi(m). 2
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 (list; graph; refs; listen; history; text; internal format)
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 * A223539 A211544 A080713

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

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Last modified February 22 13:09 EST 2018. Contains 299454 sequences. (Running on oeis4.)