When is the next "double-13 Friday"?

[Jonathan Post]

How about 5/13/2011? Found by Chris Caldwell. Is he right?  What next?

On 10/14/06, Jonathan Post <jvospost3 at gmail.com> wrote:
>
> There is a query about the next date in a sequence. Yesterday was such a
> date:  double-13 Friday: All the numbers in the numerical notation --
> 10/13/2006 -- add up to 13 as well.
>
> Dear G.L.,
>
> Should be easy in Mathematica, which I have not yet bought. I guess I'd
> start with: A101312 Number of "Friday the 13ths" in year n
> (starting at 1901).
> 2, 1, 3, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 3, 1, 1, 2, 2,
> 1, 2, 1, 2, 2, 1, 3, 1, 1, 3, 2, 1, 3, 1, 2, 2, 2, 2,
> 1, 1, 2, 2, 1, 3, 1, 1, 2, 2, 1, 2, 1, 2, 2, 1, 3, 1,
> 1, 3, 2, 1, 3, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 3, 1, 1,
> 2, 2, 1, 2, 1, 2, 2, 1, 3, 1, 1, 3, 2, 1, 3, 1, 2, 2,
> 2, 2, 1, 1, 2, 2, 1, 3, 1, 1, 2, 2, 1, 2, 1
>
> OFFSET
> 1901,1
>
> COMMENT
>
> This sequence is basically periodic with period 28
> [example: a(1901) = a(1929) = a(1957)], with "jumps"
> when it passes a non-leap-year century such as 2100
> [all centuries which are not multiples of 400]. At
>
> these points [for example, a(2101)], the sequence
> simply "jumps" to a different point in the same
> pattern, "dropping back" 12 entries [or equivalently,
> "skipping ahead" 16 entries], but still continuing
>
> with the same repeating [period 28] pattern. Every
> year has at least 1 "Friday the 13th," and no year has
> more than 3. On average, 3 of every 7 years (43%) have
> 1 "Friday the 13th," 3 of every 7 years (43%) have 2
>
> of them, and only 1 in 7 years (14%) has 3 of them.
> Conjecture: The same basic repeating pattern results
> if we seek the number of "Sunday the 22nds" or
> "Wednesday the 8ths" or anything else similar, with
>
> the only difference being that the sequence starts at
> a different point in the repeating pattern.
> 	
> EXAMPLE 	
>
> a(2004) = 2, since there were 2 "Friday the 13ths"
> that year: February 13,2004 and August 13, 2004 both
>
> fell on a Friday.
>
> MATHEMATICA 	
>
> (*Load <<Miscellaneous`Calendar` package first*) s={};
> For[n=1901, n<=2200, t=0; For[m=1, m<=12,
> If[DayOfWeek[{n, m, 13}]===Friday, t++ ]; m++ ];
> AppendTo[s, t]; n++ ]; s
>
> 	
> KEYWORD nonn
>
> AUTHOR 	
>
> Adam M. Kalman (mocha(AT)clarityconnect.com), Dec 22
> 2004
>
> ---
> honak3r at bvunet.net <http://us.f551.mail.yahoo.com/ym/Compose?To=honak3r@bvunet.net&YY=95130&y5beta=yes&y5beta=yes&order=down&sort=date&pos=0&view=a&head=b> wrote:
>
> > > It's double-13 Friday. All the
> > > numbers in the numerical notation -- 10/13/2006 --
> > add up
> > > to 13 as well.
> >
> >
> > Thanks for that, I appreciate it.
>
> >
> > What I'd like to know, is when is it going to occur
> > again?
> >
> > G. L.
>
> To: editor
> Subject: New Prime Curio about 10132006 by Post
> From: Prime Curios! automailer for
> <
> jvospost2 at yahoo.com <http://us.f551.mail.yahoo.com/ym/Compose?To=jvospost2@yahoo.com&YY=93458&y5beta=yes&y5beta=yes&order=down&sort=date&pos=0&view=a&head=b>>
>
> There has been a new curio submitted for your
> approval:
>
> 10132006 [number_id=6569]
>
> Some people fear the prime 13, especially on Fridays.
> Curiously so on 10/13/2006, whose digits concatenate
>
> as
> 10132006. <a href=
> "http://washingtontimes.com/national/20061012-115954-3697r.htm">
> For the fearful, this Friday has their number By
>
> Jennifer Harper THE WASHINGTON TIMES October 13,
> 2006</a>
>
> This is not a good day for paraskevidekatriaphobics --
> those who fear Friday the 13th. It's double-13 Friday.
> All the numbers in the numerical notation --10/13/2006
>
> -- add up to 13 as well, giving great pause to the
> superstitious. The phenomenon hasn't happened in 476
> years, said Heinrich Hemme, a physicist at Germany's
> University of Aachen who crunched the numbers to find
>
> that the double-whammy last occurred Jan. 13, 1520.
>
> "Pure chance," the good professor told the press
> yesterday.
>
> But it's not exactly TGIF for the 21 million Americans
> who fear the day. Some may not travel or even get out
>
> of bed, said Donald Dossey, a North Carolina
> psychologist who coined the term
> "paraskevidekatriaphobia" 20 years ago. He estimates
> that the nation is out $900 million in lost
> productivity because of Friday the 13th sick-outs...
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.seqfan.eu/pipermail/seqfan/attachments/20061014/ec856722/attachment-0002.htm>