Puzzle 64 is between --keyspace D450000000000000:D46fffffffffffff Let's see who solve it first..
Range completed with --stride 1111
Proof of work
16jY7qLJ7nCjNCw3vnHjsNZbswAWbjgJRE D451B2D7C5C1F338
16jY7qLJ3Dvbu1wTLpuTqpNpmeoyZu6edt D4532C684B1A0377
16jY7qLJnByZxp2wFGigyn18Q1H53TTmVa D4538334E25AE667
16jY7qLJqUPuYXpH2sG2RDLs7bkxQ8PeEJ D457720CFE8EF9B9
16jY7qLJmL7ASHkjmYxyeocgsyCGF7dLuG D4590E552E66414D
16jY7qLJX52y1TU63G3dZENuZdfbhQNMtp D45B9DA6D0CCA91C
16jY7qLJWAAv5RTtZ3RzgazoiS8hEV1sAX D463D679528F8815
16jY7qLJU8XxLVq2BM2bHBEe5vwr4Pffuc D46458AB1B9F130B
16jY7qLJHSatNNrmU6m3MRJEPuN7RiJaV7 D46B91712BD763C2
16jY7qLJQ1m34R4YBGRWRdGTdABEcyLE65 D46BE3E6992BFEC5
Next --stride 12345
Try using large primes as your strides (not something like 11111), something tells me that adding easy numbers like this is as far as you can get from the PK.
Addition is done on the stride so even keys will be searched too.