Leading least prime signatures: a(n) is in A025487 but a(n)/2 is not.

Terms

a(0) =1a(1) =6a(2) =30a(3) =36a(4) =180a(5) =210a(6) =216a(7) =900a(8) =1080a(9) =1260a(10) =1296a(11) =2310a(12) =5400a(13) =6300a(14) =6480a(15) =7560a(16) =7776a(17) =13860a(18) =27000a(19) =30030a(20) =32400a(21) =37800a(22) =38880a(23) =44100a(24) =45360a(25) =46656a(26) =69300a(27) =83160a(28) =162000a(29) =180180