A030386 - OEIS

%I #30 Nov 28 2017 11:36:28

%S 0,1,2,3,0,1,1,1,2,1,3,1,0,2,1,2,2,2,3,2,0,3,1,3,2,3,3,3,0,0,1,1,0,1,

%T 2,0,1,3,0,1,0,1,1,1,1,1,2,1,1,3,1,1,0,2,1,1,2,1,2,2,1,3,2,1,0,3,1,1,

%U 3,1,2,3,1,3,3,1,0,0,2,1,0,2,2,0,2,3,0,2,0,1,2

%N Triangle T(n,k): write n in base 4, reverse order of digits.

%H Reinhard Zumkeller, <a href="/A030386/b030386.txt">Rows n = 0..1000 of triangle, flattened</a>

%e Triangle begins:

%e 0

%e 1

%e 2

%e 3

%e 0, 1

%e 1, 1

%e 2, 1

%e 3, 1

%e 0, 2

%e 1, 2

%e 2, 2

%e 3, 2

%e 0, 3

%e 1, 3

%e 2, 3

%e 3, 3

%e 0, 0, 1

%e 1, 0, 1 ... - _Philippe Deléham_, Oct 20 2011

%p A030386_row := n -> op(convert(n, base, 4)):

%p seq(A030386_row(n), n=0..36); # _Peter Luschny_, Nov 28 2017

%t Flatten[Table[Reverse[IntegerDigits[n,4]],{n,0,50}]] (* _Harvey P. Dale_, Oct 13 2012 *)

%o (PARI) A030386(n, k=-1)=/*k<0&&error("Flattened sequence not yet implemented.")*/n\4^k%4 \\ Assuming that columns are numbered starting with k=0 as in A030308, A030341, ... \\ _M. F. Hasler_, Jul 21 2013

%o (Haskell)

%o a030386 n k = a030386_tabf !! n !! k

%o a030386_row n = a030386_tabf !! n

%o a030386_tabf = iterate succ [0] where

%o    succ []     = [1]

%o    succ (3:ts) = 0 : succ ts

%o    succ (t:ts) = (t + 1) : ts

%o -- _Reinhard Zumkeller_, Sep 18 2015

%Y Cf. A030308, A030341, A031235, A030567, A031007, A031045, A031087, A031298 for the base-2 to base-10 analogs.

%Y Cf. A007090.

%K nonn,base,tabf,less

%O 0,3

%A _Clark Kimberling_

%E Initial 0 and better name by _Philippe Deléham_, Oct 20 2011