2053059121

Appears in sequences

• a(n+1) - 3*a(n) + a(n-1) = (2/3)(1+w^(n+1)+w^(2n+2)), where w = exp(2 Pi I / 3).at n=23A071618
• a(n) = F(n-th squarefree)/product{p=primes,p|(n-th squarefree)} F(p), where F(m) is m-th Fibonacci number.at n=42A115022
• a(n) = numerator of Sum_{i=1..n} binomial(2n-i-1,i-1)/i.at n=22A175385
• Half the number of n X 2 binary arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.at n=22A185828
• Indices of triangular numbers (A000217) that are also centered pentagonal numbers (A005891).at n=15A254626
• Partial sums of the Lucas numbers of the form L(3n+2) (A163063).at n=14A307268