Odd part of the swinging factorial A056040.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =3a(5) =15a(6) =5a(7) =35a(8) =35a(9) =315a(10) =63a(11) =693a(12) =231a(13) =3003a(14) =429a(15) =6435a(16) =6435a(17) =109395a(18) =12155a(19) =230945a(20) =46189a(21) =969969a(22) =88179a(23) =2028117a(24) =676039a(25) =16900975a(26) =1300075a(27) =35102025a(28) =5014575a(29) =145422675