This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A058977 For a rational number p/q let f(p/q) = sum of distinct prime factors (A008472) of p+q divided by number of distinct prime factors (A001221) of p+q; a(n) is obtained by iterating f, starting at n/1, until an integer is reached, or if no integer is ever reached then a(n) = 0. 8
 2, 3, 2, 5, 7, 7, 2, 3, 3, 11, 7, 13, 11, 4, 2, 17, 7, 19, 3, 5, 4, 23, 7, 5, 17, 3, 11, 29, 13, 31, 2, 7, 5, 6, 7, 37, 23, 8, 3, 41, 4, 43, 4, 4, 3, 47, 7, 7, 3, 10, 17, 53, 7, 8, 11, 11, 7, 59, 13, 61, 6, 5, 2, 9, 19, 67, 5, 13, 17, 71, 7, 73, 41, 4, 23, 9, 6, 79, 3, 3, 4, 83, 4, 11, 47 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A247462 gives number of iterations needed to reach a(n). - Reinhard Zumkeller, Sep 17 2014 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 P. Schogt, The Wild Number Problem: math or fiction?, arXiv preprint arXiv:1211.6583, 2012. - From N. J. A. Sloane, Jan 03 2013 EXAMPLE f(5/1) = 5/2 and f(5/2) = 7, so a(5)=7. MATHEMATICA nxt[n_]:=Module[{s=Numerator[n]+Denominator[n]}, Total[Transpose[ FactorInteger[ s]][[1]]]/PrimeNu[s]]; Table[NestWhile[nxt, nxt[n], !IntegerQ[#]&], {n, 90}] (* Harvey P. Dale, Mar 15 2013 *) PROG (Haskell) import Data.Ratio ((%), numerator, denominator) a058977 = numerator . until ((== 1) . denominator) f . f . fromIntegral    where f x = a008472 z % a001221 z                where z = numerator x + denominator x -- Reinhard Zumkeller, Aug 29 2014 CROSSREFS Cf. A058971, A058972. Cf. A008472, A001221. Cf. A247462, A247468. Sequence in context: A192141 A092556 A092550 * A085818 A270709 A323382 Adjacent sequences:  A058974 A058975 A058976 * A058978 A058979 A058980 KEYWORD nonn,easy,nice AUTHOR N. J. A. Sloane, Jan 14 2001 EXTENSIONS More terms from Matthew Conroy, Apr 18 2001 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 July 17 21:36 EDT 2019. Contains 325109 sequences. (Running on oeis4.)