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: A097718 A075681 A034520 this_sequence A129556 A077209 A068045

Adjacent sequences: A111125 A111126 A111127 this_sequence 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).