[seqfan] Re: Left-Truncatable Primes

[D. S. McNeil]

> Here's a 49-digit
> attempt at a large example that I grew through random accretion:
>
> {26, 27, 16, 17, 12, 26, 29, 19, 17, 5, 20, 18, 1, 26, 12, 12, 6, 18, 15,
> 19, 7, 26, 29, 5, 24, 23, 23, 14, 13, 28, 7, 3, 8, 28, 22, 25, 21, 25, 23,
> 13, 25, 15, 15, 8, 12, 19, 1, 25, 19} =
> 2147186882499459649456828050886961756168069394758485971705532390689634669

If you get rid of the first few leading digits, the above base can grow to

(52, 46212444940022668197241992452430886961756168069394758485971705532390689634669)

A quick random search also found
(52, 6746999023662174120195846029574108824127823773684385612737452746013845299911)
(54, 46071685943242412300535281203072358142840379367082553572588976377500554005389531)
(55, 650379368354094724189020297139068892827323003905810462093722423851579612592910871)
(56, 19856016600622697046168651648719147208695005987453835098219736059293513408698219657)
(57, 411291914238776106750099679030284743525636385960027211524301740715056303745471477079)

A slightly more rigorous search (you can probably figure out what kind
of search from the pattern in the numbers :^) came up with

[49] 2303418823383282872134780773970068044466594767920124231049377940091821937
[50] 28626345038751211127043910773970068044466594767920124231049377940091821937
[51] 2095221435658027761570639117467039254663918621020277963324235777940091821937
[52] 24309370467878918707018427930281216552052434728043691976933793847940091821937
[53] 205796933114773097431002319487281216552052434728043691976933793847940091821937
[53] 1562624129852374490206772929487281216552052434728043691976933793847940091821937
[54] 57774036566124432190917269629487281216552052434728043691976933793847940091821937
[55] 1639255207885546514866963245527302057140940006670892871384197604055207940091821937
[56] 33040113189527178747677654505527302057140940006670892871384197604055207940091821937
[57] 294713929703207447354433415005527302057140940006670892871384197604055207940091821937
[58] 1864756828785289058994967978005527302057140940006670892871384197604055207940091821937

and then from a different seed:

[58] 40721348535931071866380064565345765542974345147939498196348936588251508860108598320183
[59] 520527358935200937965988792156972602033267557954050245952354538075484743218178598320183
[60] 38672569806629784100830978673056972602033267557954050245952354538075484743218178598320183

which is probably the best I can do for the moment.  A few more
digits, maybe, but that's it.


Doug