In my report of counts of n-digit base-3 and base-4 biquams yesterday, I neglected to point out that I was allowing leading zero digits. Thanks to David Wilson for bringing this to my attention. For the counts of n-digit base-5 biquams, allowing leading zeros, I get 0, 4, 30, 200, 1205, 6750, 36050, 187024, 954135, 4822526, ... John Layman