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 A190652 #18 Feb 16 2025 08:33:14
%S A190652 1901,1905,1906,1907,1908,1911,1912,1917,1918,1920,1922,1923,1929,
%T A190652 1933,1934,1935,1936,1939,1940,1945,1946,1948,1950,1951,1957,1961,
%U A190652 1962,1963,1964,1967,1968,1973,1974,1976,1978,1979,1985,1989,1990,1991,1992,1995,1996
%N A190652 Years with exactly two "Friday the 13ths", starting from 1901.
%H A190652 Reinhard Zumkeller, <a href="/A190652/b190652.txt">Table of n, a(n) for n = 1..1000</a>
%H A190652 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Triskaidekaphobia.html">Triskaidekaphobia</a>
%H A190652 Wikipedia, <a href="http://en.wikipedia.org/wiki/Triskaidekaphobia">Triskaidekaphobia</a>
%H A190652 <a href="/index/Ca#calendar">Index entries for sequences related to calendars</a>
%F A190652 A101312(a(n)) = 2, 1 <= A101312(n) <= 3.
%e A190652 2004 is a term, since only Feb 13 2004 and Aug 13 2004 fell on a Friday.
%t A190652 Select[Range[1901,2020],Count[Table[{#,m,13},{m,12}],_?(DayName[#] == Friday&)] == 2&] (* _Harvey P. Dale_, Oct 02 2018 *)
%o A190652 (Haskell)
%o A190652 a190652 n = a190652_list !! (n-1)
%o A190652 a190652_list = filter ((== 2) . a101312) [1901..]
%o A190652 (Python)
%o A190652 from datetime import date
%o A190652 def ok(n): return sum(date.isoweekday(date(n, m, 13)) == 5 for m in range(1, 13)) == 2
%o A190652 print(list(filter(ok, range(1901, 2000)))) # _Michael S. Branicky_, Sep 12 2021
%Y A190652 Cf. A101312, A190651, A190653.
%K A190652 nonn
%O A190652 1,1
%A A190652 _Reinhard Zumkeller_, May 16 2011