21405

Appears in sequences

• a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2*n - 2 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 3, and a(3) = 2.at n=17A049923
• Eigentriangle of Catalan triangle A033184.at n=49A172380
• Triangle whose inverse has production matrix with general term (-1)^(n-k+1)*C(k+1, n-k+1).at n=39A172381
• Sum of prime anti-divisors of n = sum of prime anti-divisors of n+1 with n > 1.at n=7A192283
• Number of length n+5 0..4 arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms.at n=1A250077
• T(n,k)=Number of length n+5 0..k arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms.at n=11A250081
• Number of length 2+5 0..n arrays with every six consecutive terms having the maximum of some two terms equal to the minimum of the remaining four terms.at n=3A250083
• Number of (n+2)X(2+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 0 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0 3 4 6 or 7.at n=4A252099
• Number of (n+2)X(5+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 0 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0 3 4 6 or 7.at n=1A252102
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 0 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0 3 4 6 or 7.at n=16A252105
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 0 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0 3 4 6 or 7.at n=19A252105
• Numbers divisible by prime(d) for each digit d in their base-9 representation, none of which may be zero.at n=51A256879
• Triangle read by rows: T(n,k) (0 <= k <= n) is the rank of the ideal I_r in the inverse semigroup D_n of all difunctional relations on an n-element set.at n=52A294432
• Numbers m that divide the alternating sum Sum_{k=1..m} (-1)^(k+1) * usigma(k).at n=12A379924