A094356 Duplicate of A087335.
4, 16, 121, 841, 1681, 5041
Offset: 1
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
3 + 1 = 4, 3*5 + 1 = 16, 3*5*8 + 1 = 121 etc. are squares.
p = 1; Do[k = 2; While[ !IntegerQ[Sqrt[p*k + 1]], k++ ]; Print[k]; p *= k, {n, 1, 9}] (* Ryan Propper *)