login
This site is supported by donations to The OEIS Foundation.

 

Logo

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A019269 Let Dedekind's psi(m) = product of (p+1)p^(e-1) for primes p, where p^e is a factor of m. Iterating psi(m) eventually results in a number of form 2^a*3^b. a(n) is the number of steps to reach such a number. 3
0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 2, 1, 1, 0, 1, 0, 2, 1, 1, 1, 1, 0, 2, 2, 0, 1, 2, 1, 1, 0, 1, 1, 1, 0, 3, 2, 2, 1, 2, 1, 2, 1, 1, 1, 1, 0, 2, 2, 1, 2, 1, 0, 1, 1, 2, 2, 2, 1, 2, 1, 1, 0, 2, 1, 2, 1, 1, 1, 1, 0, 4, 3, 2, 2, 1, 2, 2, 1, 0, 2, 2, 1, 1, 2, 2, 1, 2, 1, 2, 1, 1, 1, 2, 0, 3, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,13

COMMENTS

a(A019268(n)) = n and a(m) <> n for m < A019268(n). [Reinhard Zumkeller, Apr 12 2012]

REFERENCES

R. K. Guy, "Unsolved Problems in Number Theory", section B41.

Peter Giblin, "Primes and Programming - an Introduction to Number Theory with Computation", page 118.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

PROG

(Haskell)

a019269 n = snd $ until ((== 1) . a065333 . fst)

                        (\(x, i) -> (a001615 x, i+1)) (n, 0)

-- Reinhard Zumkeller, Apr 12 2012

CROSSREFS

Cf. A001615, A065333.

Sequence in context: A257510 A225721 A040076 * A204459 A035155 A090584

Adjacent sequences:  A019266 A019267 A019268 * A019270 A019271 A019272

KEYWORD

nonn

AUTHOR

Jud McCranie

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 21 13:36 EDT 2017. Contains 290890 sequences.