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 A080479 #8 Jan 23 2021 09:55:53
%S A080479 1,23,456,10789,1111112345,101111226789,22222222345678,
%T A080479 1022333333334569,102333344444445789,10234444455555556789,
%U A080479 1023455555666666666789,102345666677777777777889,10012345677888888888889999,1000000011111122334455678999999999
%N A080479 Smallest number formed by using all the digits (with multiplicity) of next n numbers.
%o A080479 (Python)
%o A080479 def a(n):
%o A080479 s = "".join(sorted("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1)))))
%o A080479 if '0' not in s: return int(s)
%o A080479 rz = s.rfind('0')
%o A080479 return int(s[rz+1] + s[:rz+1] + s[rz+2:])
%o A080479 print([a(n) for n in range(1, 15)]) # _Michael S. Branicky_, Jan 23 2021
%Y A080479 Cf. A053067 (next n concatenated), A080480 (largest).
%K A080479 base,easy,nonn
%O A080479 1,2
%A A080479 _Amarnath Murthy_, Mar 11 2003
%E A080479 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003