A059717 Start with decimal expansion of n; if all digits have the same parity, stop; otherwise write down the number formed by the even digits and the number formed by the odd digits and add them; repeat.
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 11, 3, 13, 5, 15, 7, 17, 9, 19, 20, 3, 22, 5, 24, 7, 26, 9, 28, 11, 3, 31, 5, 33, 7, 35, 9, 37, 11, 39, 40, 5, 42, 7, 44, 9, 46, 11, 48, 13, 5, 51, 7, 53, 9, 55, 11, 57, 13, 59, 60, 7, 62, 9, 64, 11, 66, 13, 68, 15, 7, 71, 9, 73, 11, 75
Offset: 0
Examples
For example, 59708 -> (0)8 + 597 = 605 -> 60 + 5 = 65 -> 6 + 5 = 11, stop, so a(59708) = 11.
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
Programs
-
Haskell
import Data.List (unfoldr) a059717 n = if u == n || v == n then n else a059717 (u + v) where (u,v) = foldl (\(x,y) d -> if odd d then (10*x+d,y) else (x,10*y+d)) (0,0) $ reverse $ unfoldr (\z -> if z == 0 then Nothing else Just $ swap $ divMod z 10) n -- Reinhard Zumkeller, Nov 16 2011 (corrected), Jul 05 2011 -
Mathematica
f[n_] := (id = IntegerDigits[n]; oddDigits = Select[id, OddQ]; evenDigits = Select[id, EvenQ]; Which[ oddDigits == {}, FromDigits[ evenDigits ], evenDigits == {}, FromDigits[ oddDigits ], True, FromDigits[ evenDigits ] + FromDigits[ oddDigits ]]); a[n_] := FixedPoint[f, n]; Table[a[n], {n, 0, 75}] (* Jean-François Alcover, May 31 2013 *)
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