216747218

Appears in sequences

• a(n) = (F(3*n+1) - 1)/2, where F=A000045 (the Fibonacci sequence).at n=14A049651
• First member of the Diophantine pair (m,k) that satisfies 5*(m^2 + m) = k^2 + k; a(n) = m.at n=14A077259
• Row sums of triangle A099510, so that a(n) = Sum_{k=0..n} coefficient of z^k in (1 + 2*z + z^2)^(n-[k/2]), where [k/2] is the integer floor of k/2.at n=20A099511
• Define a(1)=0, a(2)=2 then a(n) = 3*a(n-1) - a(n-2), a(n+1) = 3*a(n)-a(n-1) and a(n+2) = 3*a(n+1) - a(n) + 2.at n=20A105073
• Expansion of (1-x)^3/(1-4x+5x^2-4x^3+x^4).at n=21A109961