Numbers k such that the sum of exponents of k is equal to the greatest prime factor of k; a(1)=1.

Terms

a(0) =1a(1) =4a(2) =12a(3) =18a(4) =27a(5) =80a(6) =120a(7) =180a(8) =200a(9) =270a(10) =300a(11) =405a(12) =448a(13) =450a(14) =500a(15) =672a(16) =675a(17) =750a(18) =1008a(19) =1120a(20) =1125a(21) =1250a(22) =1512a(23) =1568a(24) =1680a(25) =1875a(26) =2268a(27) =2352a(28) =2520a(29) =2800