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 A132133 #17 Oct 26 2019 03:35:31
%S A132133 1,9,45,270,2104,16941,142245,1226146
%N A132133 Number of n-digit "Punctual Birds" (cf. A131881).
%C A132133 The number of n-digit "Early Birds" is 9*10^(n-1) - A132133(n), which is 0, 45, 630, 6896, 73059, 757755, 7773854, ... for n = 1, 2, ...
%C A132133 Here a(0) = 1 corresponds to the number 0 which is punctual in the sense that it does not occur before position 0, and which may be considered to have 0 digits for convenience: The index of 10^n in A131881 is then Sum_{k=0..n} a(k). - _M. F. Hasler_, Oct 25 2019
%e A132133 a(2) = 45 because there are 45 2-digit Punctual Birds (10, 11, 13-20, 22, 24-30, 33, 35-40, 44, 46-50, 55, 57-60, 66, 68-70, 77, 79, 80, 88 and 90)
%Y A132133 Cf. A033307, A117804, A116700, A131881, A132131, A132132.
%K A132133 base,nonn,more
%O A132133 0,2
%A A132133 _Graeme McRae_, Aug 11 2007
%E A132133 Extended to a(0) = 1 by _M. F. Hasler_, Oct 25 2019