80745

Appears in sequences

• Number of 3 X 3 integer matrices with elements in the range [ -n,n ] which represent a rotation of order 2.at n=22A053171
• Numbers k such that sigma(phi(sigma(k))) = phi(sigma(phi(k))).at n=25A067160
• Deficient numbers whose aliquot sequence is deficient, abundant, deficient, ..., etc.at n=20A234970
• Expansion of e.g.f. exp( x^2/(2 * (1-x)^2) ) / (1-x).at n=7A361596