A244426 Take the sequence of almost-natural numbers (A007376) and reverse successive subsequences of lengths 1,2,3,4,...
1, 3, 2, 6, 5, 4, 1, 9, 8, 7, 2, 1, 1, 1, 0, 5, 1, 4, 1, 3, 1, 1, 8, 1, 7, 1, 6, 1, 2, 2, 2, 1, 2, 0, 2, 9, 7, 2, 6, 2, 5, 2, 4, 2, 3, 2, 3, 1, 3, 0, 3, 9, 2, 8, 2, 3, 7, 3, 6, 3, 5, 3, 4, 3, 3, 3, 4, 3, 4, 2, 4, 1, 4, 0, 4, 9, 3, 8, 0, 5, 9, 4, 8, 4, 7, 4, 6, 4, 5, 4, 4, 7, 5, 6, 5, 5, 5, 4, 5, 3, 5, 2, 5, 1, 5
Offset: 1
Programs
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Mathematica
a[n_] := Block[{m = 0, d = n, i = 1, l, p}, While[m <= d, l = m; m = 9 i*10^(i - 1) + l; i++]; i--; p = Mod[d - l, i]; q = Floor[(d - l)/i] + 10^(i - 1); If[ p != 0, IntegerDigits[q][[p]], Mod[q - 1, 10]]]; Table[ a[ Ceiling[(Sqrt[ 8n + 1] - 1)/2]^2 - n + 1], {n, 105}]
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