Indices of centered pentagonal numbers (A005891) that are also triangular numbers (A000217).

A254627

Indices of centered pentagonal numbers (A005891) that are also triangular numbers (A000217).

Terms

    a(0) =1a(1) =2a(2) =11a(3) =28a(4) =189a(5) =494a(6) =3383a(7) =8856a(8) =60697a(9) =158906a(10) =1089155a(11) =2851444a(12) =19544085a(13) =51167078a(14) =350704367a(15) =918155952a(16) =6293134513a(17) =16475640050a(18) =112925716859a(19) =295643364940

External references