A327919 -id:A327919 - cp's OEIS frontend

A327918 The 16 pure prime dates of each non-leap year of the form concatenate(month,day) with month and day also prime numbers.

23, 211, 223, 37, 311, 313, 317, 331, 53, 523, 73, 719, 113, 1117, 1123, 1129

Offset: 1

Wolfdieter Lang, Oct 08 2019

For the numbers for leap years see A327919.
Only the months February (2), March (3), May (5), July (7) and November (11) qualify. The qualifying prime days are for month m=2: 3, 5, 7, 11, 13, 17, 19, 23; for month m = 11: 3, 5, 7, 11, 13, 17, 19, 23, 29 and for months m = 3, 5, and 7: 3, 5, 7, 11, 13, 17, 19, 23, 29, 31.
The months m = 2, 3, 5, 7, 11 contribute 3, 5, 2, 2, 4 days, respectively, adding to 16.

Cf. A165243 (first three terms), A165292 (first five terms), A165555 (first two terms), A167187 (first two terms), A327348 (m and d nonprime allowed), A327914 (with 0 before d = 1..9), A327919 (leap year), A327920 (pure prime dates of d.m form).

A327920 The 16 pure prime dates of each year of the form concatenate(day,month) with month and day also prime numbers.

Original entry on oeis.org

23, 53, 73, 113, 173, 193, 233, 293, 313, 37, 137, 197, 317, 211, 311, 2311

Offset: 1

Wolfdieter Lang, Oct 08 2019

For the case of the 16, respectively 17, pure prime dates of the form concatenate(month,day) see A327918 (non-leap years) and A327919 (leap years).
Only the three months m = 3, 7, and 11 qualify. The qualifying days are for November (m = 11): d = 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, and for months March and July (m = 3 and 7): d = 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31.
The months m = 3, 7, 11 contribute 9, 4, 3 dates, respectively, adding to 16.

Cf. A055782 (first nine terms), A055783 (first four terms), A114007 (three terms starting with n = 8). A327346 (with d and m also nonprime allowed), A327918, A327919.

Select[Flatten[Table[d*10^IntegerLength[m]+m,{m,{3,7,11}},{d,Prime[ Range[ 11]]}]],PrimeQ] (* Harvey P. Dale, May 24 2022 *)

cp's OEIS Frontend

A327918 The 16 pure prime dates of each non-leap year of the form concatenate(month,day) with month and day also prime numbers.

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