a(15) is greater than 10^7 and of the form (p^5)(q^4)rs where p, q, r and s are distinct primes.
Table of n, a(n) for n=1..14.
Will Nicholes, Iterative mapping of prime signatures.
Cf. A179216, A179222.
Sequence in context: A281645 A224211 A187026 * A103964 A199790 A088329
Adjacent sequences: A179218 A179219 A179220 * A179222 A179223 A179224
Will Nicholes, Jul 10 2010