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 A141287 #23 Feb 22 2025 22:27:06
%S A141287 1760,1788,1828,1856,1884,1924,1952,1980,2008,2036,2064,2092,2104,
%T A141287 2132,2160,2188,2228,2256,2284,2324,2352,2380,2408,2436,2464,2492,
%U A141287 2504,2532,2560,2588,2628,2656,2684,2724,2752,2780,2808,2836,2864,2892,2904,2932
%N A141287 Years in which there are five Fridays in the month of February.
%H A141287 <a href="/index/Ca#calendar">Index entries for sequences related to calendars</a>
%H A141287 <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).
%p A141287 A141287 := proc(n) nper := (n-1) mod 14 ; floor((n-1)/14)*400+op(1+nper ,[1760, 1788, 1828, 1856, 1884, 1924, 1952, 1980, 2008, 2036, 2064, 2092, 2104, 2132]) ; end proc: seq(A141287(n),n=1..80) ; # _R. J. Mathar_, Jan 25 2010
%t A141287 (* First do *) Needs["Calendar`"] (* then *) fQ[y_] := Mod[y, 4] == 0 && Mod[y, 400]!=0 && DayOfWeek[{y, 2, 1}] == Friday; Select[Range[1750, 3051], fQ@# &] (* _Robert G. Wilson v_, Jun 11 2010 *)
%t A141287 (* Second program, needing Mma version >= 9.0 *)
%t A141287 okQ[y_] := Mod[y, 4] == 0 && DayCount[{y, 1, 31}, DatePlus[{y, 3, 1}, -1], Friday] == 5;
%t A141287 Select[Range[1752, 3051, 4], okQ] (* _Jean-François Alcover_, Mar 27 2020 *)
%Y A141287 Cf. A119406 (Sun), A135795 (Mon), A143994 (Tue), A141039 (Wed), A143995 (Thu), A176478 (Sat).
%K A141287 nonn,easy
%O A141287 1,1
%A A141287 _J. Lowell_, Aug 01 2008
%E A141287 More terms using the 400-year periodicity of the Gregorian calendar by _R. J. Mathar_, Jan 25 2010