This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A236858 #15 Apr 29 2019 11:28:25
%S A236858 1,1,1,2,1,2,3,4,5,6,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,
%T A236858 11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,
%U A236858 34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60
%N A236858 Irregular table where row n contains numbers from 1 to the least common multiple (LCM) of {1, 2, ..., n}. Row 0 is given as a(0)=1.
%C A236858 Numbers 1..A003418(n) followed by numbers 1..A003418(n+1), etc., where A003418(n) gives the least common multiple (LCM) of {1, 2, ..., n} for n >= 1 and A003418(0)=1.
%C A236858 Useful when computing irregular tables like A238280. Note that as A238280 begins with row 1, it starts referring to this sequence only from a(1) onward.
%H A236858 Antti Karttunen, <a href="/A236858/b236858.txt">Rows 0..10 of the table, flattened</a>
%F A236858 a(n) = n - A236856(A236857(n)- 1).
%e A236858 The sequence can be viewed also as an irregular table that starts as:
%e A236858 0 | 1;
%e A236858 1 | 1;
%e A236858 2 | 1, 2;
%e A236858 3 | 1, 2, 3, 4, 5, 6;
%e A236858 4 | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12;
%e A236858 ...
%t A236858 Join[{1},Table[Range[LCM@@Range[n]],{n,6}]//Flatten] (* _Harvey P. Dale_, Apr 29 2019 *)
%o A236858 (Scheme) (define (A236858 n) (- n (A236856 (- (A236857 n) 1))))
%Y A236858 A003418(n) gives the last term of each row n.
%Y A236858 Cf. A220661, A236856, A236857, A238280.
%K A236858 nonn,tabf,easy
%O A236858 0,4
%A A236858 _Antti Karttunen_, Feb 27 2014