21129

Appears in sequences

• Numbers k such that z(k) = j(k), where z(k) = sopf(k - d(k)), j(k) = d(sopf(k) + k), sopf(k) = A008472(k) and d(k) = A000005(k).at n=27A063961
• Number of compositions of n with first part 1 and no equal adjacent parts; this is column 1 of the array in A096568.at n=20A096569
• a(n) = (A212146(n)-1)/2.at n=19A212147
• Number of set partitions of [n] having exactly eight pairs (m,m+1) such that m+1 is in some block b and m is in block b+1.at n=2A270962
• G.f. A(x) satisfies A(x) = 1 + x*(1-x^2)^3*A(x)^3.at n=8A389943