21252634831
domain: N
Appears in sequences
- a(n) = 4*a(n-1) - a(n-2) with a(0) = 0, a(1) = 1.at n=19A001353
- Pisot sequence E(4,15): a(n) = floor(a(n-1)^2/a(n-2)+1/2) for n>1, a(0)=4, a(1)=15.at n=17A010905
- Bisection of A001353. Indices of square numbers which are also octagonal.at n=9A028230
- a(2*n) = A028230(n), a(2*n+1) = -A067900(n+1).at n=18A110294
- a(0) = 1, a(1) = -4, a(n) = -4*a(n-1) - a(n-2) for n > 1.at n=18A125905
- Denominators of continued fraction convergents to sqrt(3)/2.at n=19A144536
- Numerators b(n) of Pythagorean approximations b(n)/a(n) to sqrt(3).at n=17A195503
- Denominator of Kirchhoff index of ladder graph L_n.at n=18A265031
- Primitive part of A001353(n).at n=18A306825
- a(n) is the greatest divisor of A001353(n) that is coprime to A001353(m) for all positive integers m < n.at n=18A309526