A190653 Years with exactly three "Friday the 13ths", starting from 1901.

1903, 1914, 1925, 1928, 1931, 1942, 1953, 1956, 1959, 1970, 1981, 1984, 1987, 1998, 2009, 2012, 2015, 2026, 2037, 2040, 2043, 2054, 2065, 2068, 2071, 2082, 2093, 2096, 2099, 2105, 2108, 2111, 2122, 2133, 2136, 2139, 2150, 2161, 2164, 2167, 2178, 2189, 2192

Offset

1,1

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Triskaidekaphobia

Wikipedia, Triskaidekaphobia

Index entries for sequences related to calendars

Formula

A101312(a(n)) = 3, 1 <= A101312(n) <= 3.

Example

2012 is a term, since only Jan 13 2012, Apr 13 2012 and Jul 13 2012 fell on Fridays.

Mathematica

Module[{mos={#[[1]], Length[#]}&/@(Flatten[Take[#, 1]&/@DateSelect[ DateRange[ {1900, 1, 1}, {2200, 12, 1}], #Day==13&&#DayName== Friday&]]// Split)}, Select[ mos, #[[2]]>2&][[All, 1]]] (* Requires Mathematica version 12 or later *) (* Harvey P. Dale, Jan 17 2021 *)

Prog

(Haskell)
a190653 n = a190653_list !! (n-1)
a190653_list = filter ((== 3) . a101312) [1901..]
(Python)
from datetime import date
def ok(n): return sum(date.isoweekday(date(n, m, 13)) == 5 for m in range(1, 13)) == 3
print(list(filter(ok, range(1901, 2193)))) # Michael S. Branicky, Sep 12 2021

Crossrefs

Cf. A101312, A190651, A190652.

Sequence in context: A273913 A190651 A237787 * A124628 A253364 A112947

Adjacent sequences: A190650 A190651 A190652 * A190654 A190655 A190656

Keyword

nonn

Author

Reinhard Zumkeller, May 16 2011

Status

approved