67921

Appears in sequences

• Expansion of 1/((1-5x)(1-9x)(1-10x)).at n=4A020494
• G.f.: (x+4*x^3+x^5)/((1-x)^2*(1-x^2)^2*(1-x^3)).at n=41A083707
• Start with 1 and repeatedly reverse the digits and add 65 to get the next term.at n=39A118163
• Euler pseudoprimes to base 5: composite integers such that abs(5^((n - 1)/2)) == 1 mod n.at n=33A262052
• Number of planar vertically indecomposable distributive lattices with n nodes.at n=31A345734
• Base-5 Euler-Jacobi pseudoprimes: odd composite k coprime to 5 such that 5^((k-1)/2) == (5/k) (mod n), where (5/k) is the Jacobi symbol (or Kronecker symbol).at n=24A375914
• Composite numbers k == 1, 9 (mod 10) such that 5^((k-1)/2) == 1 (mod k).at n=23A375915