The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A053147 When cototient function (A051953) is iterated with initial value A002110(n), a(n) = value of first (largest) power of 2 which appears in the iteration. 0
 2, 4, 8, 32, 32, 256, 32, 512, 256, 65536, 64, 512, 4096, 256, 512, 128, 16, 2048, 64, 64, 512, 8192, 256, 8192, 2048, 131072, 128, 8192, 1048576, 16, 2048, 2048, 32768, 8192, 512, 524288, 8192, 64, 16, 8192 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In these iteration chains the number of non-2-powers seem to be dominant. The sequence is not monotonic. LINKS EXAMPLE For n=10, the iteration chain of 43 terms is {6469693230, 5447823150, 4315810350, ..., 188416, 98304, 65536, 32768, ..., 4, 2, 1, 0} in which the largest power of 2 is 65536 = 2^16. For n=11 the length is 61, including 54 numbers that are not powers of 2, and 7 powers of 2, of which the largest is 64 = a(11) < a(10) = 65536. MATHEMATICA Table[SelectFirst[NestWhileList[# - EulerPhi@ # &, P, # > 0 &], IntegerQ@ Log2@ # &], {P, FoldList[Times, Prime@ Range@ 30]}] (* Michael De Vlieger, Jun 11 2018 *) CROSSREFS Cf. A002110, A051953. Sequence in context: A100083 A151406 A307611 * A128055 A061285 A194810 Adjacent sequences:  A053144 A053145 A053146 * A053148 A053149 A053150 KEYWORD more,nonn AUTHOR Labos Elemer, Feb 28 2000 EXTENSIONS More terms from Michael De Vlieger, Jun 11 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 20 20:50 EST 2021. Contains 340332 sequences. (Running on oeis4.)