23204domain: NAppears in sequencesG.f.: x(2-5x-2x^2)/(1-6x+9x^2-x^4).at n=9A106438Chebyshev transform of the second kind of the Pell numbers.at n=17A112575Number of compositions of n with strictly increasing differences.at n=47A325547Number of subsets of {1..n} containing all of their pairwise sums <= n.at n=25A326083