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A178055
Numbers representing the number of days in a month in the Gregorian calendar (modulus 7).
2
3, 1, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 1, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 0, 3, 2, 3, 2, 3, 3, 2, 3, 2, 3, 3, 1, 3, 2, 3, 2, 3, 3, 2
OFFSET
1,1
COMMENTS
Sequence first term represents January 2000. Sequence repeats after 4800 terms, representing 400 years in the Gregorian calendar system.
Actual number of days in a month can be determined by adding 28 to the value of the sequence term representing the month in question.
EXAMPLE
a(1) = 3 -> January 2000 has 31 days (3+28), a(2) = 1 -> February 2000 has 29 days (1+28), a(3) = 3 -> March 2000 has 31 days (3+28).
MATHEMATICA
dys[{y_, m_, 1}]:=If[m==12, DateDifference[{y, m, 1}, {y+1, 1, 1}], DateDifference[ {y, m, 1}, {y, m+1, 1}]][[1]]; Mod[#, 7]&/@(dys/@ Flatten[Table[{y, m, 1}, {y, 2000, 2010}, {m, 12}], 1]) (* Harvey P. Dale, Sep 04 2020 *)
CROSSREFS
Cf. A178054. If a(n) is the n-th term in A178054 and b(n) is the n-th term in A178055, then a(n) + b(n) (modulus 7) = a(n+1)
Sequence in context: A229215 A123508 A117621 * A247856 A059660 A194003
KEYWORD
easy,nonn
AUTHOR
Lyle P. Blosser (lyleblosser(AT)att.net), May 18 2010
STATUS
approved