1,1
See A109943 and the references therein for more information.
Eric Weisstein's World of Mathematics, Prime Array.
Al Zimmermann's Programming Contests. Primal Squares: The Problem
Al Zimmermann's Programming Contests. Primal Squares: Best grids for part 1 found during the contest.
Al Zimmermann's Programming Contests. Primal Squares: Part 2 solutions
a(2)=21 is the "part 2" score for the matrix
4 7
3 1
which contains two single digit primes and one even number (score:2+1)
and 9 2-digit primes: 13,17,31,37,41,43,47,71,73 score(9*2); total=3+18=21.
Cf. A032529 = all primes in the 3 X 3 record matrix, A034720 = number of candidates to be checked for primality in an n X n matrix of single digits.
Sequence in context: A180232 A075681 A034520 * A129556 A077209 A068045
Adjacent sequences: A111125 A111126 A111127 * A111129 A111130 A111131
hard,more,nonn
Hugo Pfoertner (hugo(AT)pfoertner.org), Sep 21 2005
1192 1847 are lower bounds for the next terms a(7) and a(8).
