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%I #20 Apr 26 2024 03:48:18
%S 1,2,3,4,5,6,7,8,9,17,18,19,27,28,29,37,38,39,47,48,49,57,58,59,67,68,
%T 69,77,78,79,87,88,89,97,98,99,187,188,189,197,198,199,287,288,289,
%U 297,298,299,387,388,389,397,398,399,487,488,489,497,498,499,587
%N Numbers written in base of triangular numbers where the trailing digits are made as high as possible.
%C This sequence differs from A000462 whose leading digits are made as high as possible.
%e The digits (from right to left) have values 1, 3, 6, 10, etc. (A000217), hence a(61) = 587 because 61 = 5*6 + 8*3 + 7*1.
%t A000217[n_]:=n(n+1)/2; a[n_]:=Module[{s=0}, num=n; digits={}; s=Ceiling[Root[9(#1^3+3#1^2+2#1)-6num &, 1]]; While[s>0, AppendTo[digits, d=Ceiling[(num-9(s-1)^2)/A000217[s]]]; num-=d*A000217[s]; s--]; FromDigits[digits]]; Array[a,61]
%Y Cf. A000217, A000462.
%Y 9*A000292(n) gives the number of terms with at most n digits.
%K nonn,base,easy
%O 1,2
%A _Stefano Spezia_, Apr 25 2024
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