OFFSET
1,1
COMMENTS
In a leap year the months 1, 2, ..., 12 contribute 7, 6, 6, 5, 4, 5, 5, 7, 4, 8, 4, 6 such dates. This adds to 67 prime dates. For non-leap years see the 66 prime dates given in A327348.
MATHEMATICA
Select[Flatten@ Array[Function[{m, d}, Array[FromDigits[Join[m, IntegerDigits[#]]] &, d]] @@ {IntegerDigits@ #, Which[MemberQ[{4, 6, 9, 11}, #], 30, # == 2, 29, True, 31]} &, 12], PrimeQ] (* Michael De Vlieger, Oct 03 2019 *)
CROSSREFS
Cf. A327346 (74 prime dates of the form d.m (no leading 0's for m and d), A327347 (55 prime dates of the form d.m with leading 0's for m = 1, 3, 7, 9), A327348 (non-leap year case), A327914 (58 prime dates of the form m.d in non-leap years, with leading 0 for d = 1..9), A327915 (59 prime dates like A327914 but for leap years).
KEYWORD
nonn,easy,fini,full
AUTHOR
Wolfdieter Lang, Sep 30 2019
STATUS
approved