A327346 The 74 prime dates of each year of the form concatenate(day,month) without leading zeros for month (and day), sorted by date, including duplicates.

11, 31, 41, 61, 71, 101, 131, 151, 181, 191, 211, 241, 251, 271, 281, 311, 13, 23, 43, 53, 73, 83, 103, 113, 163, 173, 193, 223, 233, 263, 283, 293, 313, 17, 37, 47, 67, 97, 107, 127, 137, 157, 167, 197, 227, 257, 277, 307, 317, 19, 29, 59, 79, 89, 109, 139, 149, 179, 199, 229, 239, 269, 211, 311, 811, 911, 1511, 1811, 2011, 2111, 2311, 2411, 2711, 3011

Offset

1,1

Comments

All these prime dates come from January, March, July, September and November, in the form d.m with no 0 in front of the months m = 1, 3, 7, and 9, with 16, 17, 16, 13 and 12 dates, respectively, which sum to 74.

There are just two duplicates, 211 (Jan. 21 and Nov. 2) and 311 (Jan. 31 and Nov. 3).

Links

Table of n, a(n) for n=1..74.

Mathematica

Select[Flatten@ Array[Function[{m, d}, Array[FromDigits[IntegerDigits[#]~Join~m] &, d]] @@ {IntegerDigits@ #, Which[MemberQ[{4, 6, 9, 11}, #], 30, # == 2, 28, True, 31]} &, 12], PrimeQ] (* Michael De Vlieger, Oct 03 2019 *)

Crossrefs

Cf. A030430 (first 16 members), A030431 (17 members, starting with n = 2), A030432 (16 members starting with n = 2), A030433 (first 13 members), A167442 (12 members starting with n = 2).

Cf. A327347 (54 prime dates d.m with leading 0 for months m = 1, 3, 7, 9), A327348 (66 prime dates m.d for non-leap years), A327349 (67 prime dates, like A327348 but for leap years), A327914 (58 prime dates m.d in non-leap years, with leading 0 for d = 1..9), A327915 (59 prime dates, like A327914, but for leap years).

Sequence in context: A038351 A068871 A004615 * A030430 A059313 A040975

Adjacent sequences: A327343 A327344 A327345 * A327347 A327348 A327349

Keyword

nonn,easy,fini,full

Author

Wolfdieter Lang, Sep 30 2019

Status

approved