OFFSET
1,1
COMMENTS
See A109943 and the references therein for more information.
1192 and 1847 are lower bounds for the next terms a(7) and a(8).
LINKS
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
EXAMPLE
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.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Hugo Pfoertner, Sep 21 2005
STATUS
approved