121023

Appears in sequences

• Numbers n such that phi(reverse(n)) = sigma(n).at n=17A070835
• Coefficients of x^n in the (n-1)-th iteration of (x + x^2) for n>=1.at n=7A112319
• Triangle, read by rows, that transforms rows into diagonals in the table of coefficients of successive iterations of x+x^2 (cf. A122888).at n=28A166900
• Number of nonequivalent ways (mod D_3) to place 4 points on an n X n X n triangular grid so that no two of them are on the same row, column or diagonal.at n=13A283115