

A190653


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


4



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
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OFFSET

1,1


LINKS



FORMULA



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 !! (n1)
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


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



