|
%I #9 Jul 11 2015 08:20:07
%S 1,1,1,1,2,2,2,2,2,2,1,1,2,2,3,3,3,3,2,3,3,3,3,3,2,3,3,3,3,3,3,3,3,3,
%T 2,3,1,3,3,3,3,3,3,3,2,4,3,3,3,3,4,4,4,3,4,4,4,4,2,3,4,3,4,4,3,4,2,3,
%U 4,4,4,3,3,4,3,4,3,2,4,4,4,3,3,4,4,3,4,3,4,3,4,4,4,4,3,4,3,4,4,4,2,2,3,3,4
%N Number of distinct digits needed to write the n-th triangular number in decimal representation.
%C 0 < a(n) <= 10;
%C a(n) = A043537(A000217(n)).
%H Reinhard Zumkeller, <a href="/A118668/b118668.txt">Table of n, a(n) for n = 0..10000</a>
%e n=99: 99*(99+1)/2 = 4950 -> a(99) = #{0,4,5,9} = 4;
%e see A119033 for an overview of sequences with terms composed of not more than 3 distinct digits.
%e n=100: 100*(100+1)/2 = 5050 -> a(100) = #{0,5} = 2;
%t Length[Union[IntegerDigits[#]]]&/@Accumulate[Range[0,110]] (* _Harvey P. Dale_, Jul 23 2012 *)
%o (Haskell)
%o a118668 = a043537 . a000217
%o a118668_list = map a043537 a000217_list
%o -- _Reinhard Zumkeller_, Jul 11 2015
%Y Cf. A000217, A043537, A045914, A213517, A213518, A255678.
%K nonn,base
%O 0,5
%A _Reinhard Zumkeller_, May 19 2006
|
