A213182 -id:A213182 - cp's OEIS frontend

A227407 Prime numbers representing a date in "condensed European notation" DDMMYY.

10103, 10111, 10133, 10139, 10141, 10151, 10159, 10163, 10169, 10177, 10181, 10193, 10211, 10223, 10243, 10247, 10253, 10259, 10267, 10271, 10273, 10289, 10301, 10303, 10313, 10321, 10331, 10333, 10337, 10343, 10357, 10369, 10391, 10399, 10427, 10429, 10433

Offset: 1

Shyam Sunder Gupta, Sep 22 2013

For February, the number of days will be 28 only, as the year cannot be a leap year if DDMMYY is to be a prime number.

The sequence is finite, with 3111 terms. The largest term is a(3111)=311299.

			a(1)=10103 is prime and represents a date in DDMMYY format as 010103.

Shyam Sunder Gupta, Table of n, a(n) for n = 1..3111

Cf. A213182, A227409.

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], AppendTo[t, a]], {d, 1, b}], {m, 1, 12}, {y, 1, 99}]; Union[t]

A213184 Numbers which may represent a date in "condensed American notation" MMDDYY.

Original entry on oeis.org

10100, 10101, 10102, 10103, 10104, 10105, 10106, 10107, 10108, 10109, 10110, 10111, 10112, 10113, 10114, 10115, 10116, 10117, 10118, 10119, 10120, 10121, 10122, 10123, 10124, 10125, 10126, 10127, 10128, 10129, 10130, 10131, 10132, 10133, 10134, 10135, 10136, 10137, 10138, 10139, 10140

Offset: 1

M. F. Hasler, Feb 28 2013

The "may" in the definition should clarify that, e.g., 22900 is in the sequence since it may represent a date (Feb. 29), but not necessarily in any century (e.g., in 2000 but not in 1900), but 22900+k is present only for k=0 (mod 4).

The sequence is finite, with 366*25 + 365*75 terms, cf. comment from G. Resta in A213182. The largest term is a(36525)=123199.

			a(1)=10100 represents, e.g., Jan 01 1900 (or Jan 01 2000).
a(100)=10199 (for Jan 01 1999) is followed by a(101)=10200 (for Jan 02 2000).
a(3100)=13199 (for Jan 31 1999) is followed by a(3101)=20100 (for Feb 01 2000).

Cf. A213182, A106605, A107273, A107275; A210883, A210884, A210885.

A227411 Palindromic prime numbers representing a date in "condensed European notation" DDMMYY.

Original entry on oeis.org

10301, 10501, 10601, 30103, 30203, 30403, 30703, 30803, 31013, 70207, 70507, 70607, 90709, 91019

Offset: 1

Shyam Sunder Gupta, Sep 22 2013

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

			a(1)=10103 is prime and represents a date in DDMMYY format as 010103.

Cf. A213182, A227407, A227410.

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]

Incorrect a(15)-a(32) from Vincenzo Librandi, Sep 23 2013 removed. - Jon Perry, Sep 24 2013

cp's OEIS Frontend

A227407 Prime numbers representing a date in "condensed European notation" DDMMYY.

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A213184 Numbers which may represent a date in "condensed American notation" MMDDYY.

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A227411 Palindromic prime numbers representing a date in "condensed European notation" DDMMYY.

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