OFFSET
0,2
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
P. Schogt, The Wild Number Problem: math or fiction?, arXiv preprint arXiv:1211.6583 [math.HO], 2012. - From N. J. A. Sloane, Jan 03 2013
FORMULA
a(A214866(n)) = 0. - Reinhard Zumkeller, Mar 11 2013
EXAMPLE
3/1 -> 3/4 -> 12/7 -> 84/10=42/5 -> 210/11 -> 2310/5 = 462 so a(3)=462.
84/1 -> 84/13 -> 273/4 -> 273/4 -> ... so a(84) = 0.
MATHEMATICA
f[Rational[p_, q_]] := p*q/(Total[ IntegerDigits[p]] + Total[ IntegerDigits[q]]); f[n_Integer] := n/(1 + Total[ IntegerDigits[n]]); a[n_] := If[ IntegerQ[ r = NestWhile[f, n, Not[#1 == #2 || #1 != #2 && IntegerQ[#2]]&, 2]], r, 0]; Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Apr 03 2013 *)
PROG
(Haskell)
import Data.Ratio ((%), numerator, denominator)
a059175 n = f [n % 1] where
f xs@(x:_) | denominator y == 1 = numerator y
| y `elem` xs = 0
| otherwise = f (y : xs)
where y = (numerator x * denominator x) %
(a007953 (numerator x) + a007953 (denominator x))
-- Reinhard Zumkeller, Mar 11 2013
(PARI) f2(p, q) = p*q/(sumdigits(p)+sumdigits(q));
f1(r) = f2(numerator(r), denominator(r));
loop(list) = {my(v=Vecrev(list)); for (i=2, #v, if (v[i] == v[1], return(1)); ); }
a(n) = {if (n==0, return(0)); my(ok=0, m=f2(n, 1), list=List()); while(denominator(m) != 1, m = f1(m); listput(list, m); if (loop(list), return (0)); ); return(m); } \\ Michel Marcus, Feb 09 2022
CROSSREFS
KEYWORD
base,easy,nonn,nice
AUTHOR
Floor van Lamoen, Jan 15 2001
EXTENSIONS
Corrected and extended by Naohiro Nomoto, Jul 20 2001
STATUS
approved