23900

Appears in sequences

• a(n) = A064835(n)/2.at n=21A064836
• Number of labeled digraphs with n arcs and with no vertex of indegree 0.at n=6A122419
• Riordan array (1/(1 + 5*x + x^2), x/(1 + 5*x + x^2))^(-1); inverse of Riordan array A123967.at n=22A125906
• a(n) = (number of compositions of n into odd parts) - (number of compositions of n into distinct parts).at n=23A282694
• Numbers k such that 5*10^k + 41 is prime.at n=21A291605
• Number of level n squares on a Sierpinski carpet that are enclosed in a circle with the same center and diameter.at n=5A293288
• Triangle read by rows: T(n,k) is the number of unlabeled connected weakly graded (ranked) posets with n elements and rank k.at n=39A361954