39771

Appears in sequences

• Odd composite n such that phi(n) * sigma(n) is one less than a square.at n=22A015722
• Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=1, r=5, I={0,1,3}.at n=49A079957
• Number of distinct solutions of sum{i=1..3}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 2..n-2.at n=20A180826
• Numbers generated by recursive procedure a(n) = nozero(a(n-1) * 3), in which the function nozero(x) removes all zeros from x, starting with a(1) = 1.at n=20A243845
• Magic sums of 3 X 3 semimagic squares composed of odd squares.at n=16A269297
• Place two n-gons with radii 1 and 2 concentrically, forming an annular area between them. Connect all the vertices with line segments that lie entirely within that area. Then a(n) is the number of edges in that figure.at n=24A337702