181815

Appears in sequences

• Numerators in continued fraction [0; 1, 3, 1, 3, 1, 3, ...].at n=15A136210
• G.f.: M(F(x)) is a power series in x consisting entirely of positive integer coefficients such that M(F(x) - x^k) has negative coefficients for k>0, where M(x) = 1 + x*M(x) + x*M(x)^2 is the g.f. of the Motzkin numbers A001006.at n=35A251571
• Numbers n such that the sum of the divisors of n equals the fourth power of the sum of the digits of n.at n=11A260598
• p-INVERT of the positive integers, where p(S) = 1 - 3*S.at n=7A290902