22421

Appears in sequences

• Interprimes which are of the form s*prime, s=7.at n=23A075282
• Semiprimes that are the sum of the first n semiprimes for some n.at n=30A092190
• Number of compositions of n in which the largest part is equal to the number of parts.at n=20A098124
• a(n) = 1 + (n-1) + (n-2)*[(n-3)/2] + (n-3)*[(n-4)/2]*[(n-5)/3] + (n-4)*[(n-5)/2]*[(n-6)/3]*[(n-7)/4] +... where [x] = floor(x), with summation extending over the initial [n/2+1] products only.at n=23A207644
• Numbers k such that k divides 1 + Sum_{j=1..k} prime(j)^17.at n=15A233556
• Number of partitions p of n not including ceiling(mean(p)) as a part.at n=41A241337
• On a spirally numbered square grid, with labels starting at 1, this is the number of the last cell that a (1,n) leaper reaches before getting trapped, or -1 if it never gets trapped.at n=5A323471
• Triangle read by rows: T(m,n) is the label of the ending square of an (m,n)-leaper (a generalization of a chess knight) when it can no longer move, starting on a board with squares spirally numbered, starting at 1; 1 <= n < m. Each move is to the lowest-numbered unvisited square.at n=10A323750