3128164186

Appears in sequences

• Number of ways of choosing at most n-1 items from a set of size 2*n+1.at n=16A008549
• a(n) = 2^(n-1) - binomial(n, floor(n/2)).at n=32A093387
• Number of walks f length n on a square lattice ending with x > 0 and y > 0.at n=17A186648
• The number of set partitions of {1,2,...,n} into exactly two subsets A,B such that the greatest common divisor of |A| and |B| = 1.at n=32A194924
• a(n) = 2^(n-1) + ((1+(-1)^n)/4)*binomial(n, n/2) - binomial(n, floor(n/2)).at n=33A294175