The pi-based arithmetic derivative of the double factorial of n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =12a(5) =19a(6) =128a(7) =193a(8) =1600a(9) =2997a(10) =20224a(11) =37692a(12) =319488a(13) =552366a(14) =5164032a(15) =10853055a(16) =103268352a(17) =198691110a(18) =2199453696a(19) =4050806490a(20) =49934499840a(21) =102089892240