The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A175125 a(n) is the number of numbers m such that the number of iterations of r -> r - (largest divisor d < r) needed to reach 1 starting at r = m is equal to n. 5
1, 1, 2, 3, 5, 9, 13, 23, 36, 65, 100, 175, 275, 468, 760, 1266, 2077, 3454, 5690, 9449, 15547, 25709, 42459, 70181, 115947, 191509, 316570, 523087, 864406, 1428174, 2359266 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
EXAMPLE
Example (a(4)=5): There are five numbers (7,9,10,12,16) with 4 steps of defined iteration: 7-1=6, 6-3=3, 3-1=2, 2-1=1; 9-3=6, 6-3=3, 3-1=2, 2-1=1; 10-5=5, 5-1=4, 4-2=2, 2-1=1; 12-6=6, 6-3=3, 3-1=2, 2-1=1; 16-8=8, 8-4=4, 4-2=2, 2-1=1.
PROG
(PARI) a064097(n)={my(k=1, d=divisors(n), r=n-d[#d-1]); while(r>1, d=divisors(r); r-=d[#d-1]; k++); k};
my(c=vector(50)); for(k=2, 2^20, j=a064097(k); c[j]++); concat([1], c[1..20]) \\ Hugo Pfoertner, Mar 23 2020
CROSSREFS
Sequence in context: A336631 A228129 A369695 * A171925 A186946 A057225
KEYWORD
nonn,more
AUTHOR
Jaroslav Krizek, Feb 15 2010
EXTENSIONS
a(8)-a(27) from Hugo Pfoertner, Mar 23 2020
a(28)-a(30) from Robert G. Wilson v, Apr 05 2020
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 29 11:52 EDT 2024. Contains 372940 sequences. (Running on oeis4.)