Primes of the form a^a + b^b + c^c + d^d.

Terms

a(0) =7a(1) =13a(2) =59a(3) =311a(4) =337a(5) =769a(6) =3137a(7) =3389a(8) =9631a(9) =46691a(10) =49783a(11) =49789a(12) =139969a(13) =143093a(14) =823601a(15) =826673a(16) =826699a(17) =870253a(18) =916859a(19) =16777729a(20) =16780369a(21) =16780601a(22) =16823903a(23) =16827001a(24) =17600761a(25) =17600813a(26) =18427427a(27) =33557561a(28) =33604213a(29) =34378231