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%I #5 Sep 03 2013 13:49:43
%S 0,1,21,3,45,15,6,78,28,91,10,1128,120,136,1431,15,1653,171,1830,190,
%T 120,21,1225,231,2415,253,1326,276,28,2926,300,231,325,3321,2346,351,
%U 36,378,3828,3916,406,741,4278,435,4465,45,465,4753,1485,496,2850,351,528
%N Least triangular number T(k) that contains the consecutive digits of n, where T(k) = k*(k+1)/2.
%C The indices, k, of these T(k) for each n are at A118388.
%H T. D. Noe, <a href="/A118389/b118389.txt">Table of n, a(n) for n = 0..10000</a>
%e ====================
%e n k T(k)
%e ====================
%e 0 0 0
%e 1 1 1
%e 2 6 21
%e 3 2 3
%e 4 9 45
%e 5 5 15
%e 6 3 6
%e 7 12 78
%e 8 7 28
%e 9 13 91
%e 10 4 10
%t nn = 68; t = Table[0, {nn}]; n = 0; found = 0; While[found < nn, n++; k = n (n + 1)/2; d = IntegerDigits[k]; s = Sort[FromDigits /@ Flatten[Table[Partition[d, i, 1], {i, Length[d]}], 1]]; i = 1; While[i <= Length[s] && s[[i]] <= nn, If[t[[s[[i]]]] == 0, t[[s[[i]]]] = k; found++]; i++]]; t = Join[{0}, t] (* _T. D. Noe_, Sep 03 2013 *)
%Y Cf. A000217, A118388.
%K base,easy,nonn
%O 0,3
%A _Jonathan Vos Post_, Apr 26 2006
%E Corrected by _T. D. Noe_, Sep 03 2013
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