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

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

Offset: 1

Author

Wolfdieter Lang, Oct 08 2019

Keywords

• nonn
• easy
• fini
• full

Comments

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.

Crossrefs

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.

Programs

Mathematica

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