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 A227411 Palindromic prime numbers representing a date in "condensed European notation" DDMMYY. 1
 10301, 10501, 10601, 30103, 30203, 30403, 30703, 30803, 31013, 70207, 70507, 70607, 90709, 91019 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For February, the number of days will be 28 only, as year cannot be a leap year for DDMMYY to be a prime number. The sequence is finite, with 14 terms. The largest term is a(14)=91019. There are no 6-digit solutions - the month must be 11 and the day cannot start with a 0 or a 2. Nor can the day start with a 1 because this makes the palindrome of the form 1x11x1 - divisible by 1001. This leaves only 301103, which is 11*31*883, so not prime. - Jon Perry, Sep 23 2013 LINKS EXAMPLE a(1)=10103 is prime and represents a date in DDMMYY format as 010103. MATHEMATICA palindromicQ[n_] := TrueQ[IntegerDigits[n] == Reverse[IntegerDigits[n]]]; t = {}; Do[If[m < 8, If[OddQ[m], b = 31, If[m == 2, b = 28, b = 30]], If[OddQ[m], b = 30, b = 31]]; Do[a = 100 m + y + 10000 d; If[PrimeQ[a] && palindromicQ[a], AppendTo[t, a]], {d, 1, b}], {m, 1, 12}, {y, 1, 99}]; Union[t] CROSSREFS Cf. A213182, A227407, A227410. Sequence in context: A187937 A154089 A227410 * A100502 A099746 A083438 Adjacent sequences:  A227408 A227409 A227410 * A227412 A227413 A227414 KEYWORD nonn,base,fini,full,less AUTHOR Shyam Sunder Gupta, Sep 22 2013 EXTENSIONS Incorrect a(15)-a(32) from Vincenzo Librandi, Sep 23 2013 removed. - Jon Perry, Sep 24 2013 STATUS approved

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Last modified June 20 05:01 EDT 2019. Contains 324229 sequences. (Running on oeis4.)