Numbers k such that phi(k) + phi(k+3) = phi(k+1) + phi(k+2).

Terms

a(0) =1a(1) =5a(2) =7a(3) =11a(4) =17a(5) =22a(6) =88a(7) =292a(8) =847a(9) =1337a(10) =1691a(11) =7367a(12) =10385a(13) =15430a(14) =51215a(15) =93401a(16) =132535a(17) =211817a(18) =282725a(19) =358852a(20) =359905a(21) =382955a(22) =486772a(23) =507725a(24) =580262a(25) =664870a(26) =700532a(27) =1691081a(28) =1972691a(29) =2637712