Squares of composite numbers k such that sigma(k) (sum of divisors of k, A000203) is a prime.

A065404

Squares of composite numbers k such that sigma(k) (sum of divisors of k, A000203) is a prime.

Terms

    a(0) =16a(1) =64a(2) =729a(3) =2401a(4) =4096a(5) =15625a(6) =28561a(7) =65536a(8) =83521a(9) =262144a(10) =279841a(11) =531441a(12) =707281a(13) =3418801a(14) =4826809a(15) =9765625a(16) =24137569a(17) =28398241a(18) =38950081a(19) =47458321a(20) =244140625a(21) =260144641a(22) =887503681a(23) =1073741824a(24) =1387488001a(25) =2655237841

External references