Thanks, everybody. I see what my error was. (Such a stupid error, too.) When I wrote down the list of differences between the primes, I had put that 17-13=6. Is this sequence worth submitting? Thanks, Leroy Quet [ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] ) ]