a(1) = 6 and then the smallest triangular numbers, larger than the previous term, such that sum of two neighbors is also a triangular number.
A072521
a(1) = 6 and then the smallest triangular numbers, larger than the previous term, such that sum of two neighbors is also a triangular number.
Terms
- a(0) =6a(1) =15a(2) =21a(3) =45a(4) =91a(5) =990a(6) =1711a(7) =365085a(8) =401856a(9) =713415a(10) =785631a(11) =1079715a(12) =1326006a(13) =2355535a(14) =2888406a(15) =5137615a(16) =5666661a(17) =5764710a(18) =9550635a(19) =9921285a(20) =10934826a(21) =19434495a(22) =21421785a(23) =23622501a(24) =42003195a(25) =46315500a(26) =82349361a(27) =146384605a(28) =152259975a(29) =171578550
External references
- oeis: A072521