53545

Appears in sequences

• a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-3)*a(3) for n >= 4, with initial terms 1, 2, 1, 1.at n=15A025243
• a(n) = Sum_{k=0..2n-2} T(n,k) * T(n,k+2), with T given by A027113.at n=4A027142
• Number of n-digit numbers with nonzero multiplicative digital root 3.at n=6A051814
• Natural numbers written out with their digits grouped in sets of 5 (leading zeros omitted).at n=19A091341
• Triangle read by rows: number of 0-1-2 trees (i.e., ordered trees with vertices of outdegrees 0, 1, or 2) with n edges and exactly k vertices that have 2 children, both being leaves (n >= 0, 0 <= k <= floor((n+2)/4)).at n=38A126191
• Number of partitions of n where the difference between consecutive parts is at most 7.at n=44A238867
• Triangle read by rows: T(n,k) is the number of bargraphs of semiperimeter n having k levels. A level in a bargraph is a maximal sequence of two or more adjacent horizontal steps; it is preceded and followed by either an up step or a down step.at n=47A273344
• a(n) = a(n-1) + a(n-2) + 2 a(floor(n/2)) + 3 a(floor(n/3)) + ... + n a(floor(n/n)), where a(0) = 1, a(1) = 2, a(2) = 3.at n=16A298370
• Number of intersection points when every pair of vertices of a row of n adjacent congruent rectangles are joined by an infinite line.at n=21A347750