21154

Appears in sequences

• Numbers k such that sigma(k) = sigma(k+11).at n=12A015881
• Triangle T, read by rows, such that the matrix inverse satisfies: [T^-1](n,k) = -(k+1)*T(n-1,0) for n>k>=0, with T(n,n)=1 for n>=0.at n=29A112911
• Column 1 of triangle A112911.at n=6A112912
• Least integer b>2n+1 such that the numbers written as [1,3,...,2n-1,2n+1] and [2n+1,2n-1,...,3,1] in base b are both prime.at n=36A218465
• Partition the j digits of n into blocks of k, with 1 <= k <= j-1, starting at left and multiply. Sum of these numbers equals n.at n=8A275171
• a(n) = Bell(n) + n - 2 (cf. A000110).at n=8A338735
• Numbers that are the sum of four fourth powers in exactly two ways.at n=43A344193
• a(n) = Sum_{k=1..n} sigma_2(k) * floor(n/k).at n=34A356042
• Coefficients in the power series A(x) such that: 1 = Sum_{n=-oo..+oo} x^(2*n+1) * (1 - x^n)^(n+1) * A(x)^n.at n=10A356783