Numbers k such that phi(k)*sigma(k) is a triangular number.

Terms

a(0) =1a(1) =2a(2) =9a(3) =11a(4) =23a(5) =118a(6) =373a(7) =556a(8) =1332a(9) =2420a(10) =3081a(11) =5251a(12) =7642a(13) =12671a(14) =116836a(15) =127627a(16) =135861a(17) =172676a(18) =198912a(19) =365408a(20) =421902a(21) =426710a(22) =901273a(23) =921736a(24) =954068a(25) =1001396a(26) =1003333a(27) =1006567a(28) =1077452a(29) =1161754