A036103 A look-and-say sequence: each term summarizes the previous two terms.
0, 1, 1110, 4110, 145120, 1524124120, 2534425120, 354413624120, 16355433523120, 26454463424120, 36456453523120, 46457443522120, 1736556443522120, 2736556433623120, 2756553463623120, 2766552473622120
Offset: 0
Examples
a(26) = 39283736554483723130; a(27) = 39384726554493622120 = first term of first period; a(28) = 39383736455493622120; a(143) = 39283746553473823130 = last term of first period != a(26); a(144) = 39384726554493622120 = first term of second period = a(27); a(145) = 39383736455493622120 = a(28).
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 0..611 = 5 periods
- Index to sequences related to say what you see
Programs
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Haskell
import Data.List (sort, group); import Data.Function (on) a036103 n = a036103_list !! n a036103_list = 0 : 1 : map (read . concatMap say . group . reverse . sort) (zipWith ((++) `on` show) a036103_list $ tail a036103_list) where say w = (show $ length w) ++ [head w] -- Reinhard Zumkeller, Oct 05 2015 -
Mathematica
a[0] = 0; a[1] = 1; a[n_] := a[n] = Reverse /@ (Join[a[n-2] // IntegerDigits, a[n-1] // IntegerDigits] // Tally // SortBy[#, First]& // Reverse) // Flatten // FromDigits; Array[a, 16, 0] (* Jean-François Alcover, Jul 13 2016 *)
Comments