20832

Appears in sequences

• Number of permutation groups of degree n; also number of conjugacy classes of subgroups of symmetric group S_n; also number of molecular species of degree n.at n=13A000638
• a(n) = n*(n+1)*(2*n+1)/3.at n=31A006331
• Numbers n such that 54 'Reverse and Add' steps are needed to reach a palindrome.at n=4A065321
• Consider the mapping f(x/y) = (x+y)/(2xy) where x/y is a reduced fraction. Beginning with x_0 = 1 and y_0 = 2, repeated application of this mapping produces a sequence of fractions x_n/y_n; a(n) is the n-th denominator.at n=4A081476
• Numbers k such that sigma(k) divides k^2.at n=20A090777
• Numbers that can be expressed as the difference of the squares of primes in exactly five distinct ways.at n=21A092001
• Let b(0)=1; b(1)=1; b(n+2)=(e^g+1/e^g)*b(n+1)-b(n). a(n)=floor(b(n)).at n=18A093608
• a(n) = (3*n+1)*(5*n+1).at n=37A144459
• Numbers that are divisible by the product of the digit-sums of their neighbors.at n=32A152826
• Numbers of the form p^5*q*r*s where p, q, r, and s are distinct primes.at n=24A179704
• a(n) = Sum_{k=0..n-1} C(n-1,k)^(n-k) * n/(n-k).at n=5A181077
• Maximum value of sigma(x) * sigma(y) * sigma(z), where x + y + z = n.at n=40A211219
• The Wiener index of the tetrameric 1,3-adamantane TA(n) (see the Fath-Tabar et al. reference).at n=6A216106
• Triangle read by rows: T(n,k) is the number of n-tuples with sum k + n whose i-th element is a positive integer <= prime(i), 0 <= k < A070826(n).at n=64A239738
• Number of compositions of n with exactly 2 transitions between different parts.at n=36A244714
• Numbers n such that sigma(n+sigma(n)) = 4*sigma(n).at n=41A246911
• Number of length 1+2 0..n arrays with no three consecutive terms having the sum of any two elements equal to twice the third.at n=26A248462
• Number of length 1+4 0..n arrays with every five consecutive terms having four times some element equal to the sum of the remaining four.at n=10A249657
• Number of (n+1)X(1+1) arrays of permutations of 0..n*2+1 filled by rows with each element moved a city block distance of 1 or 2, and rows and columns in increasing lexicographic order.at n=7A263582
• Relative of Hofstadter Q-sequence: a(n) = max(0, n+20830) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.at n=2A283887