OFFSET
1,1
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Triskaidekaphobia
Wikipedia, Triskaidekaphobia
EXAMPLE
1902 is a term, since only Jun 13 1902 fell on a Friday.
MATHEMATICA
Select[Range[1901, 2001], Count[Table[DayName@{#, m, 13}, {m, 12}], Friday]==1&] (* Giorgos Kalogeropoulos, Sep 12 2021 *)
PROG
(Haskell)
a190651 n = a190651_list !! (n-1)
a190651_list = filter ((== 1) . 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)) == 1
print(list(filter(ok, range(1901, 2001)))) # Michael S. Branicky, Sep 12 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, May 16 2011
STATUS
approved