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%I #15 Dec 17 2024 06:32:31
%S 11,13,17,19,113,127,131,23,29,211,223,227,31,37,311,313,317,331,41,
%T 43,47,419,421,53,59,521,523,61,67,613,617,619,71,73,79,719,727,83,89,
%U 811,821,823,827,829,97,911,919,929,101,103,107,109,1013,1019,1021,1031,113,1117,1123,1129,127,1213,1217,1223,1229,1231
%N The 66 prime dates in each non-leap year of the form concatenate (month,day) without leading zeros for days.
%C The months m = 1, 2, ..., 12 contribute 7, 5, 6, 5, 4, 5, 5, 7, 4, 8, 4, 6 such dates respectively. This adds up to 66 prime dates. In leap years there is the additional date 229 (see A327349).
%t Select[Flatten@ Array[Function[{m, d}, Array[FromDigits[Join[m, IntegerDigits[#]]] &, d]] @@ {IntegerDigits@ #, Which[MemberQ[{4, 6, 9, 11}, #], 30, # == 2, 28, True, 31]} &, 12], PrimeQ] (* _Michael De Vlieger_, Oct 03 2019 *)
%Y 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), A327349 (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).
%K nonn,easy,fini,full
%O 1,1
%A _Wolfdieter Lang_, Sep 30 2019