
COMMENTS

Same as A094858 (which has much more information about the problem), except that we now we allow an arbitrary alphabet.
For even n it seems that the maximum is attained for X = 123412341234..., Y = 432143214321..., giving values : (conjectured) maximum number of maximumlengthcommonsubsequences of 2 strings of length 2*n over an arbitrary (infinite) alphabet f(2*n) = 2,4,10,28,78,220,624,1780,5100,14668,.. Note that (3*f(2*n)f(2*n+2))/2 gives 1,1,1,3,7,18,46,120,316,841,2257,6103,16611,45475,125139,.. which is A026107. Is there an explanation for this?
