20669

Appears in sequences

• a(n) = floor((a(n-2)*a(n-1))/(a(n-1)+a(n-2))) + a(n-1) + a(n-2), a(0) = 0, a(1) = 1, a(2) = 1, ...at n=18A096080
• n+p(n)+p(p(n)) is a square, where p(n) is the n-th prime.at n=11A116011
• (L)-sieve transform of A004767 = {3,7,11,15,...,4n-1,...}.at n=31A155167
• Number of (n+1)X(2+1) 0..2 arrays with the maximum plus the minimum minus the upper median minus the lower median of every 2X2 subblock equal.at n=3A237161
• Number of (n+1)X(4+1) 0..2 arrays with the maximum plus the minimum minus the upper median minus the lower median of every 2X2 subblock equal.at n=1A237163
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with the maximum plus the minimum minus the upper median minus the lower median of every 2X2 subblock equal.at n=11A237167
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with the maximum plus the minimum minus the upper median minus the lower median of every 2X2 subblock equal.at n=13A237167
• Number of binary matrices with 3 distinct columns and any number of nonzero rows with n ones in every column and rows in nonincreasing lexicographic order.at n=21A331390
• a(n) is the number of distinct triangles whose sides do not pass through a grid point and whose vertices are three points of an n X n grid.at n=30A372217
• Number of integer compositions of n whose leaders of strictly increasing runs are distinct.at n=24A374687
• Irregular table read by rows: Place n equally spaced points on the circumference of a circle of radius r and then connect each pair of points with straight lines whose intersections create A007569(n) - n additional points. Draw a circle of radius r around each of the A007569(n) points. T(n,k) is the number of k-sided regions, k>=2, formed from all circle intersections.at n=50A374828
• a(n) is the Frobenius number for the set { binomial(m,k), k=1..m-1 } where m = A024619(n).at n=3A389479