Ormiston pairs: Difference between revisions
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For this, we would like to be able to test if a prime number is the first value in an Ormiston pair:
<syntaxhighlight lang=J> isorm=: -:&(/:~)&":&> 4 p: ]</syntaxhighlight>
We could also use a routine to organize pairs of numbers as moderate width lines of text:
<syntaxhighlight lang=J> fmtpairs=: {{ names <@([,',',])&":/"1 y}}</syntaxhighlight>
Then the task becomes:
<syntaxhighlight lang=J> fmtpairs (,. 4 p:]) p:30{.I. isorm i.&.(p:inv) 1e6
1913,1931 18379,18397 19013,19031 25013,25031
34613,34631 35617,35671 35879,35897 36979,36997
37379,37397 37813,37831 40013,40031 40213,40231
40639,40693 45613,45631 48091,48109 49279,49297
51613,51631 55313,55331 56179,56197 56713,56731
58613,58631 63079,63097 63179,63197 64091,64109
65479,65497 66413,66431 74779,74797 75913,75931
76213,76231 76579,76597
+/isorm i.&.(p:inv) 1e6 NB. number of Ormiston pairs less than 1e6
382
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