21910

Appears in sequences

• Weird numbers: abundant (A005101) but not pseudoperfect (A005835).at n=39A006037
• Coordination sequence for MgZn2, Mg position.at n=37A009939
• a(n) = Sum{T(n,k)}, k = 0,1,...,n, where T is the array in A026148.at n=10A026164
• Unitary weird numbers: unitary abundant (A034683) but not unitary pseudoperfect (A293188).at n=37A064114
• Solutions y of the Mordell equation y^2 = x^3 - 3a^2 + 1 for a = 0,1,2, ... (solutions x are given by the sequence A000466).at n=14A173202
• T(n, k) = k^n*U(n, (1/k + k)/2) + (n + 1)^(k - 1)*U(k - 1, (1/(n + 1) + n + 1)/2), where U(n,x) is the n-th Chebyshev polynomial of the second kind, square array read by antidiagonals (n >= 0, k >= 1).at n=37A173590
• T(n, k) = k^n*U(n, (1/k + k)/2) + (n + 1)^(k - 1)*U(k - 1, (1/(n + 1) + n + 1)/2), where U(n,x) is the n-th Chebyshev polynomial of the second kind, square array read by antidiagonals (n >= 0, k >= 1).at n=43A173590
• T(n,k)=Number of length n+4 0..k arrays with every five consecutive terms having the maximum of some two terms equal to the minimum of the remaining three terms.at n=36A254698
• Number of length 1+4 0..n arrays with every five consecutive terms having the maximum of some two terms equal to the minimum of the remaining three terms.at n=8A254699
• Number of nX4 0..1 arrays with every element unequal to 0, 1, 2, 5 or 7 king-move adjacent elements, with upper left element zero.at n=8A304922
• Nonexponential weird numbers: nonexponential abundant numbers (A348604) that are not equal to the sum of any subset of their nonexponential divisors.at n=33A348631
• (1+e)-weird numbers: (1+e)-abundant numbers k such that no subset of the aliquot (1+e)-divisors of k sums to k.at n=34A349285
• Weird untouchable numbers.at n=10A357326