a(n) is the product of the distinct nonzero quadratic residues of n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =12a(6) =8a(7) =4a(8) =28a(9) =1080a(10) =540a(11) =36a(12) =12960a(13) =44352a(14) =2160a(15) =36a(16) =1797120a(17) =524160a(18) =22619520a(19) =2880a(20) =1088640a(21) =4790016000a(22) =465813504a(23) =6912a(24) =5096577024a(26) =5477472000a(27) =2419200a(29) =124104960000a(31) =244800a(32) =143187264000