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!)
A074347 Smallest number requiring n steps to reach 0 when iterating the function: f(n)=abs(lpd(n)-Lpf(n)), where lpd(n) is the largest proper divisor of n and Lpf(n) is the largest prime factor of n. 1
1, 2, 3, 12, 13, 52, 53, 131, 271, 811, 1601, 2711, 8111, 13997, 34589, 74551, 147773, 310567, 621227, 1230343, 2627759, 4921373, 10741931, 24965191, 45887291, 111477631, 183638843, 394195667, 788380493, 1576798931 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
2*10^9 < a(31) <= 2938669883. a(32) <= 7511549827. a(33) <= 11754740251. a(34) <= 30050593523. - Donovan Johnson, Dec 22 2010
LINKS
Jason Earls, Smarandache iterations of the first kind on functions involving divisors and prime factors, in Smarandache Notions Journal (2004), Vol. 14.1, page 259.
PROG
(PARI) {m=25; z=11000000; v=listcreate(m); for(i=1, m, listinsert(v, -1, i)); for(n=1, z, c=1; b=1; k=n; while(b&&c<=m, d=divisors(k); i=matsize(d)[2]-1; p=if(i>0, d[i], 1); q=if(k==1, 1, vecmax(component(factor(k), 1))); a=abs(p-q); if(a==0, b=0, k=a; c++)); if(a==0, if(v[c]<0, v[c]=n; print1([c, n])))); print(); for(i=1, m, print1(v[i], ", "))}
CROSSREFS
Cf. A075660.
Sequence in context: A102660 A081347 A309176 * A102034 A102150 A039588
KEYWORD
more,nonn
AUTHOR
Jason Earls, Sep 23 2002
EXTENSIONS
Four more terms from Klaus Brockhaus, Oct 01 2002
a(24)-a(30) from Donovan Johnson, Dec 22 2010
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 March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)