- --- In primenumbers@yahoogroups.com, "djbroadhurst" <david.broadhurst@...> wrote:
>

C130 factorization completed this morning (cado-nfs winner vs ecm).

>

> > F(263): one composite factor remaining (in progress).

>

> Here I used GNFS on the C130.

>

> David

>

Finally :

F(263) =

2^2

11

941

88079

40541279

53849801

3709997079374701

23529341871144986702279

7270487490315018281073601513510602536818804246566820732218199

790942341954447264420872400154902667291367695120485038995898872524619

711892421814353474455471503465724397364909744377767780766071778400352308618205366660863738451363497318680099295967052261874590114183928845236941340734473602381665606275060651

JL ---In primenumbers@yahoogroups.com, <thefatphil@...> wrote:

> You only chose that target after

> the arrow had landed, I'm sure.It happened thus:

1) I determined to factorize F(n)=((n^2-9)/4)^2-5 for

n <= 300, completely. As later shown in "factordb", I succeeded.2) Meanwhile I ran OpenPFGW on n in [301,600], hoping for a

quick outlier and found none.3) I estimated the probability of an easily discoverable

completely factorization for n>600 and found it to be small.4) Recalling how I had once been caught out before by

a "probably no more" heuristic, I set a lone process running on

n in [601, 10000] so as not to be caught out again by Jens.5) When I later looked and pfgw.log, it had found a hit at

n=608.So yes, Phil, you are quite correct that the puzzle was set

after this finding. However the heuristic that I gave was

made prior to my discovery, else I would not have said that

I was surprised.The point that you are making (I think) is that I do such

expsriments often and only notice when the result is unexpected.

I don't tell folk about all the boring times when a negative

heuristic is borne out by a null result. That is the selectioneffect.

David

`(guilty of not boring folk with what is routine)`