Primes with digital product = 4.

Terms

a(0) =41a(1) =4111a(2) =11411a(3) =12211a(4) =21121a(5) =21211a(6) =22111a(7) =112121a(8) =1114111a(9) =11111141a(10) =11141111a(11) =111112121a(12) =111121121a(13) =112111211a(14) =112112111a(15) =121111121a(16) =121112111a(17) =122111111a(18) =212111111a(19) =1111111411a(20) =1111411111a(21) =11111121121a(22) =11111121211a(23) =11111211121