21862

Appears in sequences

• Let c(k) denote the k-th composite number and p(k) the k-th prime number; then a(n) = Sum_{i=n*(n-1)/2+1 .. n*(n+1)/2} c(i) - Sum_{i=1..n} p(i).at n=33A024850
• Number of partitions satisfying (cn(1,5) <= cn(2,5) and cn(1,5) <= cn(3,5) and cn(4,5) <= cn(2,5) and cn(4,5) <= cn(3,5)).at n=48A036803
• Triangle T(n,k) read by rows; given by [0,1,0,1,0,1,0,1,...] DELTA [1,1,1,2,1,3,1,4,1,5,1,6,...], where DELTA is Deléham's operator defined in A084938.at n=50A085838
• Bond series for first parallel moment of Kagome lattice.at n=11A120546
• Number of 2's in row n of the Kolakoski fan A143477.at n=26A143588
• Number of (n+1)X(1+1) 0..4 arrays with every 2X2 subblock summing to a prime.at n=2A251508
• Number of (n+1)X(3+1) 0..4 arrays with every 2X2 subblock summing to a prime.at n=0A251510
• T(n,k)=Number of (n+1)X(k+1) 0..4 arrays with every 2X2 subblock summing to a prime.at n=3A251515
• T(n,k)=Number of (n+1)X(k+1) 0..4 arrays with every 2X2 subblock summing to a prime.at n=5A251515
• Number of (n+2)X(n+2) 0..2 arrays with every 3X3 subblock row, column, diagonal and antidiagonal sum not equal to 0 3 or 4.at n=3A252067
• Number of (n+2) X (4+2) 0..2 arrays with every 3X3 subblock row, column, diagonal and antidiagonal sum not equal to 0 3 or 4.at n=3A252071
• T(n,k)=Number of (n+2)X(k+2) 0..2 arrays with every 3X3 subblock row, column, diagonal and antidiagonal sum not equal to 0 3 or 4.at n=24A252075
• Partial sums of A255283.at n=51A255428
• Numbers k such that 445*2^k+1 is prime.at n=28A323151