2390391

Appears in sequences

• a(n) = 3^n*(3^n-1)/2.at n=7A026121
• Number of reversible strings with n beads of 3 colors. If more than 1 bead, not palindromic.at n=13A032086
• Expansion of x^2/((3*x-1)*(3*x^2-1)).at n=15A167993
• Triangular numbers of the form p*w, where p is a prime number and w is a prime power (A025475).at n=26A225674
• Triangular numbers divisible by the square of the sum of their digits.at n=25A243008
• Cogrowth sequence of the 18-element group S3 X C3 = <S,T,U | S^3, T^2, U^3, (ST)^2, [S,U], [T,U]>.at n=16A378109