Alphabetic length of a divide-and-conquer approach to the regular expression for permutations of n symbols.

A320460

Alphabetic length of a divide-and-conquer approach to the regular expression for permutations of n symbols.

Terms

    a(0) =1a(1) =4a(2) =15a(3) =48a(4) =190a(5) =600a(6) =2205a(7) =6720a(8) =29988a(9) =95760a(10) =364980a(11) =1108800a(12) =4813380a(13) =15135120a(14) =57432375a(15) =172972800a(16) =892371480a(17) =2916033120a(18) =11616348744a(19) =35384469120a(20) =162510369840a(21) =514937142720

External references