Least k>0 such that a centered polygonal number nk(k+1)/2+1 is a perfect square; or -1 if no such number exists.
A120744
Least k>0 such that a centered polygonal number nk(k+1)/2+1 is a perfect square; or -1 if no such number exists.
Terms
- a(0) =2a(1) =-1a(2) =1a(3) =3a(4) =2a(5) =7a(6) =15a(7) =1a(8) =16a(9) =8a(10) =14a(11) =4a(12) =5a(13) =15a(14) =1a(15) =2a(16) =5a(17) =-1a(18) =6a(19) =3a(20) =2a(21) =39a(22) =6a(23) =1a(24) =21a(25) =7a(26) =110a(27) =3a(28) =15a(29) =7
External references
- oeis: A120744