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%I #6 Jul 13 2013 12:04:35
%S 1,1,1,1,2,1,1,2,1,1,2,2,1,1,1,1,1,2,2,1,3,1,2,2,2,1,1,3,1,1,1,2,3,1,
%T 2,3,1,1,1,1,2,2,1,3,1,1,1,2,1,3,1,1,3,1,1,2,2,1,1,3,1,1,3,2,1,1,1,3,
%U 1,1,2,3,1,1,2,2,2,1,2,3,1,1,2,3,1,2
%N Triangle read by rows: A007651 expanded into single digits.
%C A007651(n) = sum{T(n,k)*10^(A005341(n)-k): k=1..A005341(n)}.
%H Reinhard Zumkeller, <a href="/A220424/b220424.txt">Rows n = 1..25 of triangle, flattened</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a>
%e . Initial rows A007651
%e . 1: 1 1
%e . 2: 1,1 11
%e . 3: 1,2 12
%e . 4: 1,1,2,1 1121
%e . 5: 1,2,2,1,1,1 122111
%e . 6: 1,1,2,2,1,3 112213
%e . 7: 1,2,2,2,1,1,3,1 12221131
%e . 8: 1,1,2,3,1,2,3,1,1,1 1123123111
%e . 9: 1,2,2,1,3,1,1,1,2,1,3,1,1,3 12213111213113 .
%o (Haskell)
%o import Data.List (group)
%o a220424 n k = a220424_tabf !! (n-1) !! (k-1)
%o a220424_row n = a220424_tabf !! (n-1)
%o a220424_tabf = iterate
%o (concatMap (\xs -> [head xs, length xs]) . group) [1]
%Y Cf. A005341 (row lengths), A034002 (method A version).
%K nonn,base,tabf
%O 1,5
%A _Reinhard Zumkeller_, Dec 15 2012
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