%I #2 Mar 30 2012 17:31:12
%S 1,3,6,10,1,1,7,11,2,2,0,6,4,4,1,9,6,7,10,7,9,10,1,0,1,8,4,1,10,7,1,2,
%T 0,1,10,9,1,8,8,1,9,10,2,0,2,2,7,10,2,4,8,3,4,9,3,7,0,3,0,7,4,9,4,4,8,
%U 4,4,10,7,5,2,0,5,10,9,6,8,8,6,9,10,7,0,2,7,7,10,8,4,8,8,4,9,9,7,0,9,0,7,10
%N Write the natural numbers in base 13 in a triangle with k digits in the k-th row, as shown below. Sequence gives the leading diagonal.
%C 1
%C 23
%C 456
%C 789A
%C BC101
%C 112131...
%t t = Flatten[ IntegerDigits[ Range[1900], 13]]; t[[Table[n(n + 1)/2, {n, 100}]]]
%Y Cf. A104606, A104607, A104608, A104609, A104610, A104611, A104612, A104613, A091425, A104614, A104615, A104617, A104618, A104619, A104620.
%K base,nonn
%O 1,2
%A _Robert G. Wilson v_, Mar 16 2005