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.
%I A338819 #20 Jul 01 2023 09:29:00 %S A338819 1,2,0,0,2,3,0,0,0,3,0,0,0,3,4,0,0,0,0,4,0,0,0,0,4,0,0,0,0,4,5,0,0,0, %T A338819 0,0,5,0,0,0,0,0,5,0,0,0,0,0,5,0,0,0,0,0,5,6,0,0,0,0,0,0,6,0,0,0,0,0, %U A338819 0,6,0,0,0,0,0,0,6,0,0,0,0,0,0,6,0,0,0,0,0,0,6,7,0 %N A338819 The entries in the rows of the n X n identity matrix, multiplied by the size of the matrix (n). %e A338819 For every identity matrix of size n starting with n=1, append n*(each entry of each row of the matrix), e.g., n=1 -> 1, n=2 -> 2,0,0,2, so the first 5 terms of the sequence are 1,2,0,0,2. %o A338819 (Python) %o A338819 import numpy as np %o A338819 def n_id_sequence(iterations): %o A338819 sequence = [] %o A338819 for i in range(1,iterations+1): %o A338819 matrix = i*(np.identity(i)) %o A338819 for row in matrix: %o A338819 for entry in row: %o A338819 sequence.append(int(entry)) %o A338819 return sequence %Y A338819 Cf. A191747 (with 1's), A191748 (locations of nonzero terms), A056520 (start location of each matrix). %K A338819 nonn,easy %O A338819 1,2 %A A338819 _Julia Zimmerman_, Nov 10 2020