Generalizing recklessly from the single example, 7 of 9,
I conjectured that
borgnum n
would be the greatest prime less than n^2
Looking for a J expression took me to:
borgnum=:p:@(<:@(p:^:_1))@*:
whence the 1st 10 borg numbers are
3 7 13 23 31 47 61 79 97 113
What was pleasing, of course, was the way p:^:_1 gave just what I wanted.
I checked OEIS.org, and, indeed, the sequence is there, A053001, not, alas,
identified as the borg numbers.
Sent using Hushmail
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
