13250218

Appears in sequences

• a(n) = 2*a(n-1) + a(n-2), with a(0) = 1, a(1) = 2, a(2) = 4.at n=19A052542
• Numbers k such that 2*k^2 - 4 is a square.at n=9A075870
• Series ratios converge alternately to sqrt(2) and 1+sqrt(1/2).at n=38A082766
• Sylvester dividends for Pell numbers.at n=37A105606
• Numerators of "Farey fraction" approximations to sqrt(2).at n=39A119016
• Numerators of principal and intermediate convergents to 2^(1/2).at n=36A143607
• Numerators of the upper principal and intermediate convergents to 2^(1/2).at n=18A143609
• Numerators of fractions in a 'zero-transform' approximation of sqrt(2) by means of a(n) = (a(n-1) + c)/(a(n-1) + 1) with c=2 and a(1)=0.at n=19A163271
• a(n) = tau(n)*Pell(n), where tau(n) = A000005(n), the number of divisors of n.at n=18A204270
• a(n) = Pell(n)*A001227(n) for n >= 1, where A001227(n) is the number of odd divisors of n.at n=18A209445