A327347 The 54 prime dates of each year of the form concatenate(day,month) with leading zero for months 1, 3, 7, 9 (no leading zero for days).

101, 401, 601, 701, 1201, 1301, 1601, 1801, 1901, 2801, 3001, 103, 503, 1103, 1303, 2003, 2203, 2503, 2803, 2903, 107, 307, 607, 907, 1307, 1607, 1907, 2207, 2707, 109, 409, 509, 709, 809, 1009, 1109, 1409, 1609, 1709, 2309, 2609, 2909, 211, 311, 811, 911, 1511, 1811, 2011, 2111, 2311, 2411, 2711, 3011

Offset

1,1

Comments

All these dates come from January, March, July, September and November, sorted this d.m way, with 11, 9, 9, 13 and 12 dates, respectively, summing to 54. Note that all September dates without leading zero of month m = 9 from A327346 survive after inserting the 0. The November dates coincide, of course.

Links

Table of n, a(n) for n=1..54.

Mathematica

Select[Flatten@ Map[Function[{m, d},  Array[FromDigits[IntegerDigits[#]~Join~m] &, d]] @@ {PadLeft[IntegerDigits@ #, 2], Which[MemberQ[{4, 6, 9, 11}, #], 30, # == 2, 28, True, 31]} &, Select[Range[1, 12, 2], CoprimeQ[#, 10] &]], PrimeQ] (* Michael De Vlieger, Oct 03 2019 *)

Crossrefs

Cf. A062800 (first 11 members), A101780 (9 members, starting with n = 2), A166547 (9 members, starting with n = 2), A166560 (first 13 members), A167442 (12 members, starting with n = 2), repectively.

Cf. A327346 (74 prime dates d.m without leading 0 for month), 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 for non-leap years, with leading 0 for d = 1..9), A327915 (59 prime dates, like A327914, but for leap years).

Sequence in context: A142264 A142136 A158192 * A062800 A323178 A031698

Adjacent sequences: A327344 A327345 A327346 * A327348 A327349 A327350

Keyword

nonn,easy,fini,full

Author

Wolfdieter Lang, Sep 30 2019

Status

approved