# dead sequence 0 0 1 1 2 3 3 13 4 68 5 420 6 3015 7 24541 8 223884 9 2263381 10 25121075 11 303716281 12 3973432728 13 55931774473 14 842950049823 15 13543132571641 16 231076203767720 17 4172914800390601 # dead sequence