

A008685


Lengths of months in the Gregorian calendar.


9



31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 28, 31
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OFFSET

1,1


COMMENTS

To make the definition unambiguous, consider these as starting from January 2001 (or, equivalently, AD 1 in the proleptic Gregorian calendar). [Charles R Greathouse IV, Sep 28 2011]


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Index entries for sequences related to calendars
Index entries for linear recurrences with constant coefficients, order 4800.


FORMULA

a(n) = a(n4800). [Charles R Greathouse IV, Sep 28 2011]


MATHEMATICA

year1 = 2001; year2 = 2100;
PreviousDate[#, "Day"][[1, 3]]& /@ Flatten[Table[{#, m, 1}, {m, Append[ Range[2, 12], 1]}]& /@ Range[year1, year2], 1] (* JeanFrançois Alcover, Aug 01 2018 *)


PROG

(PARI) v=[]; for(n=1, 50, v=concat(v, [31, if(n%4(n%100==0&&n%400), 28, 29), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31])); v
(Haskell)
a008685 n = a008685_list !! (n1)
a008685_list = concatMap t [1..] where
t y = [31, 28 + leap, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
where leap = if mod y 4 == 0 &&
(mod y 100 > 0  mod y 400 == 0) then 1 else 0
 Reinhard Zumkeller, Jun 19 2015


CROSSREFS

Cf. A061251.
Sequence in context: A299558 A291471 A276992 * A162156 A141529 A022987
Adjacent sequences: A008682 A008683 A008684 * A008686 A008687 A008688


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane.


STATUS

approved



