1,1

See A109943 and the references therein for more information.

1192 and 1847 are lower bounds for the next terms a(7) and a(8).

Table of n, a(n) for n=1..6.

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: A075681 A212257 A034520 * A213827 A129556 A077209

Adjacent sequences: A111125 A111126 A111127 * A111129 A111130 A111131

hard,more,nonn

Hugo Pfoertner, Sep 21 2005

approved