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A031087 Triangle T(n,k): write n in base 9, reverse order of digits.

%I A031087 #23 Jan 23 2019 17:04:11
%S A031087 0,1,2,3,4,5,6,7,8,0,1,1,1,2,1,3,1,4,1,5,1,6,1,7,1,8,1,0,2,1,2,2,2,3,
%T A031087 2,4,2,5,2,6,2,7,2,8,2,0,3,1,3,2,3,3,3,4,3,5,3,6,3,7,3,8,3,0,4,1,4,2,
%U A031087 4,3,4,4,4,5,4,6,4,7,4,8,4,0,5,1,5,2,5,3,5,4,5
%N A031087 Triangle T(n,k): write n in base 9, reverse order of digits.
%H A031087 Reinhard Zumkeller, <a href="/A031087/b031087.txt">Rows n = 0..1000 of triangle, flattened</a>
%o A031087 (PARI) A031087(n, k=-1)=/*k<0&&error("Flattened sequence not yet implemented.")*/n\9^k%9 \\ Assuming that columns are numbered starting with k=0 as in A030308, A030567 and others. - _M. F. Hasler_, Jul 21 2013
%o A031087 (Haskell)
%o A031087 a031087 n k = a031087_row n !! (k-1)
%o A031087 a031087_row n | n < 9     = [n]
%o A031087               | otherwise = m : a031087_row n' where (n',m) = divMod n 9
%o A031087 a031087_tabf = map a031087_row [0..]
%o A031087 -- _Reinhard Zumkeller_, Jul 07 2015
%Y A031087 Cf. A030308, A030341, A030386, A031235, A030567, A031007, A031045, A031298 for the base-2 to base-10 analogs.
%Y A031087 Cf. A031076, A007095.
%K A031087 nonn,base,tabf,less
%O A031087 0,3
%A A031087 _Clark Kimberling_
%E A031087 Initial 0 and better name by _Philippe Deléham_, Oct 20 2011