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 A008684 #26 Mar 03 2022 12:36:52
%S A008684 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,
%T A008684 27,28,29,30,31,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,
%U A008684 22,23,24,25,26,27,28,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
%N A008684 Dates of successive days in Gregorian calendar.
%C A008684 Starting with January and assuming not a leap year. - _Harvey P. Dale_, Sep 24 2012
%H A008684 Reinhard Zumkeller, <a href="/A008684/b008684.txt">Table of n, a(n) for n = 1..365</a>
%H A008684 <a href="/index/Ca#calendar">Index entries for sequences related to calendars</a>
%t A008684 Needs["Calendar`"]; Transpose[Table[DaysPlus[{2014,1,1},n],{n,0,364}]][[3]] (* _Harvey P. Dale_, Apr 26 2014 *)
%t A008684 DateRange[{2021,1,1},{2021,12,31}][[All,3]] (* _Harvey P. Dale_, Mar 03 2022 *)
%o A008684 (Haskell)
%o A008684 a008684 n = a008684_list !! (n-1)
%o A008684 a008684_list = concatMap (enumFromTo 1)
%o A008684 [31,28,31,30,31,30,31,31,30,31,30,31]
%o A008684 -- _Reinhard Zumkeller_, Jun 23 2013
%K A008684 nonn,nice,fini,full
%O A008684 1,2
%A A008684 _N. J. A. Sloane_