Numbers k such that sigma(k) and phi(k) are both triangular numbers.

Terms

a(0) =1a(1) =2a(2) =22a(3) =3051a(4) =3219a(5) =3393a(6) =5057a(7) =8653a(8) =75618a(9) =95675a(10) =100503a(11) =102949a(12) =104714a(13) =287826a(14) =438547a(15) =522339a(16) =537159a(17) =688050a(18) =2191200a(19) =2317118a(20) =2418548a(21) =2507683a(22) =2599128a(23) =3212964a(24) =4534573a(25) =5367797a(26) =6047913a(27) =6302639a(28) =7689149a(29) =13758296