15290740089domain: NAppears in sequencesa(n) = 2*A000129(n) - 1.at n=26A133654a(n)=a(n-1)+3a(n-2)+a(n-3).at n=28A137199The index of the first of two consecutive positive triangular numbers (A000217) the sum of which is equal to the sum of four consecutive positive triangular numbers.at n=12A262490