21778

Appears in sequences

• a(n) = Sum_{k=0..6} binomial(n,k).at n=17A008859
• Numbers k such that sigma(k) = sigma(k+11).at n=13A015881
• Numbers k such that k and k^2 use only the digits 1, 2, 4, 7 and 8.at n=28A136997
• Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having exactly k entries that are midpoints of 321 patterns (0 <= k <= n-2 for n >= 2; k=0 for n=1).at n=30A145879
• Second diagonal of triangle in A145879.at n=6A182542
• Riordan matrix (1/(1-4x),(1-sqrt(1-4x))/2).at n=59A187926
• Triangle T(n,k), read by rows, given by (1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...) DELTA (0, 0, 1, 1, 2, 2, 3, 3, 4, 4, ...) where DELTA is the operator defined in A084938.at n=46A202992
• The number of 1 X n Haunted Mirror Maze puzzles with a unique solution where mirror orientation is fixed.at n=8A204090
• Number of nX2 0..2 arrays with exactly floor(nX2/2) elements equal to at least one horizontal, vertical or antidiagonal neighbor, with new values introduced in row major 0..2 order.at n=6A222913
• T(n,k)=Number of nXk 0..2 arrays with exactly floor(nXk/2) elements equal to at least one horizontal, vertical or antidiagonal neighbor, with new values introduced in row major 0..2 order.at n=29A222918
• T(n,k)=Number of nXk 0..2 arrays with exactly floor(nXk/2) elements equal to at least one horizontal, vertical or antidiagonal neighbor, with new values introduced in row major 0..2 order.at n=34A222918
• a(n) = number of subsets of {1,2,...,n} that contain more primes than nonprimes.at n=17A369780
• a(n) = Sum_{k=0..n} binomial(3*n-1,k).at n=6A387033