A260915 Prime number days: prime numbers that can be interpreted as an ISO date.

10000103, 10000121, 10000223, 10000303, 10000511, 10000609, 10000721, 10000723, 10000813, 10000819, 10000831, 10001009, 10001107, 10001119, 10001203, 10001207, 10001209, 10001213, 10001221, 10001227, 10001231, 10010101, 10010113, 10010213, 10010227, 10010311, 10010317, 10010323, 10010401

Offset

1,1

Comments

An ISO date is in the format YYYY-MM-DD.

The last term of this sequence is 99991207.

Links

Christian Perfect, Table of n, a(n) for n = 1..24974

MEI Maths item of the month.

Date and time format - ISO 8601.

Example

20150821 belongs to this sequence because it is prime and represents the 21st of August 2015.

Mathematica

d = Sort@ Join[Flatten[Plus[{100, 300, 500, 700, 800, 1000, 1200}, #] & /@ Select[Range[1, 31, 2], ! Mod[#, 5] == 0 &]], Flatten[Plus[{200, 400, 600, 900, 1100}, #] & /@ Select[Range[1, 29, 2], ! Mod[#, 5] == 0 &]]]; Select[Flatten[Plus[If[Or[Mod[#, 10000000] == 0, Mod[#, 40000] == 0 && ! Mod[#, 1000000] == 0], d, Delete[d, 25]], #] & /@ (10000 Range[1000, 1001])], PrimeQ] (* Michael De Vlieger, Aug 04 2015 *)
Select[10000#[[1]]+100#[[2]]+#[[3]]&/@DateRange[{1000, 1, 1}, {1001, 12, 31}], PrimeQ] (* Harvey P. Dale, Apr 15 2026 *)

Prog

(Python)
import datetime
def prime_number_days():
   j = 0
   date = datetime.date(1000, 1, 1)
   while date.year<2100:
      x = int(date.strftime("%Y%m%d"))
      while primes[j]<x:
         j += 1
      if primes[j]==x:
         yield x
      date += datetime.timedelta(days=1)

Crossrefs

Cf. A000040 (prime numbers).

Sequence in context: A017515 A017647 A182749 * A072144 A087510 A173002

Adjacent sequences: A260912 A260913 A260914 * A260916 A260917 A260918

Keyword

nonn,easy,fini,base

Author

Christian Perfect, Aug 04 2015

Status

approved