749976

Appears in sequences

• Number of (12345, 13245, 21345, 23145, 31245, 32145)-avoiding permutations.at n=10A054872
• Riordan array (2-2*x-sqrt(1-8*x+4*x^2), (1-2*x-sqrt(1-8*x+4*x^2))/2).at n=45A121576