20930

Appears in sequences

• When expressed in base 2 and then interpreted in base 7, is a multiple of the original number.at n=35A062848
• Even numbers k such that the central binomial coefficient A000984(k, k/2) is divisible by k^2.at n=10A080395
• Triangle read by rows: T(n,m) = number of m-block proper covers (without empty blocks and without multiple blocks) of a labeled n-set (n>=2, 2<=m<=2^n-2).at n=21A095421
• Numbers k such that sigma(k) and phi(k) are both palindromes.at n=8A113929
• Antidiagonal sums of triangle A124428.at n=21A124429
• Number of 12-core partitions of n.at n=58A192061
• Coefficient of x in the reduction by x^2 -> x+1 of the polynomial p(n,x) defined at Comments.at n=15A192976
• Numbers such that the sum of the largest and the smallest prime divisor equals the sum of the other distinct prime divisors.at n=30A199745
• Primitive (squarefree) elements of A199745.at n=15A200145
• Number of pairs of intersecting diagonals in the interior and exterior of a regular n-gon.at n=20A211380
• Number of intersections of diagonals in the interior and exterior of a regular n-gon.at n=20A211383
• Number of (w,x,y,z) with all terms in {1,...,n} and w+x+y=|x-y|+|y-z|.at n=43A212678
• Triangle read by rows: T(n,k) is the total number of parts of size k^2, 1 <= k <= n, in the set of partitions of an n X n square lattice into squares, considering only the list of parts.at n=45A226906
• The least k such that the polynomial cyclotomic(k,x) has n different coefficients.at n=27A231611
• a(n) = 7*binomial(4*n + 7, n)/(4*n + 7).at n=5A233658
• Expansion of (1 + 2*x + 2*x^2) / (1 - x)^6.at n=12A244882
• a(n) = n*(n + 11)*(n + 22)*(n + 33)/24.at n=13A264448
• E.g.f. satisfies: A(x - Integral A(x) dx) = x + Integral A(x) dx.at n=5A277403
• a(n) = 5*(3*n+1)*(9*n+8)/2 (n>=0).at n=17A304508
• Squarefree numbers m such that the equation x*(x+1)*(x+2) = m*y^2 has more than one solution (x,y) with x>0 and y>0.at n=9A335715