1854720

Appears in sequences

• Numbers which can be expressed as product of a number and its reversal in at least three different ways.at n=3A066590
• Numbers which can be expressed as the product of a number and its reversal in four different ways.at n=2A066598
• Triangle read by rows, related to A055129 (repunits in base k).at n=53A107893
• a(1) = 1; for n > 1, a(n) = sigma(sum of the previous terms) where sigma(k) = sum of the divisors of k.at n=20A165929
• G.f.: Sum_{n>=0} (n+x)^n * x^n / (1 + n*x + x^2)^n.at n=9A187742
• Number of elements of order n in simple Mathieu group M_23.at n=10A284872