18846

Appears in sequences

• Alternating Engel expansion of Pi.at n=11A014014
• Pierce expansion for 4 - Pi.at n=11A061233
• Number of binary strings of length n with equal numbers of 001 and 010 substrings.at n=16A164141
• Initial members of abundant quadruplets, i.e., values of k such that (k, k+2, k+4, k+6) are all abundant numbers.at n=33A231089
• Numbers m such that k*phi(n) = Sum_{j|n} sigma(j), where k >= 1 is an integer.at n=26A243373
• G.f.: (1 + x) * (1 + x^2) * (1 + x^3) * Product_{k>=1} (1 + x^k).at n=49A329384
• a(n) is the number of regions formed by n-secting the angles of a nonagon (enneagon).at n=33A335781
• G.f. A(x,y) = Sum_{n>=0} x^n/(1-y)^(2*n+1) * Sum_{k=0..3*n} T(n,k)*y^k satisfies: y = Sum_{n=-oo..+oo} (-1)^n * x^(n*(n+1)/2) * A(x,y)^n.at n=40A355870
• Number of regions in a graph of n adjacent rectangles in a row with all possible diagonals drawn, as in A306302, but without the rectangles' edges which are perpendicular to the row.at n=17A369175