18525

Appears in sequences

• 9-gonal (or enneagonal) pyramidal numbers: a(n) = n*(n+1)*(7*n-4)/6.at n=25A007584
• Denominators of convergents to Pi by Farey fractions.at n=31A063673
• Take pairs (a, b), sorted on a, such that T(a)+T(b)=concatenation of a and b, where T(k) is the k-th triangular number A000217(k). Sequence gives values of a.at n=29A096031
• Number of permutations of n distinct letters (ABCD...) each of which appears 5 times and having n-2 fixed points.at n=38A123296
• Numbers k such that 2*k-1, 4*k-1, 6*k-1 and 8*k-1 are primes.at n=14A124487
• Number of (not necessarily indecomposable) Hermitian self-dual additive codes over GF(9) of length n.at n=8A196419
• Odd 9-gonal (nonagonal) pyramidal numbers.at n=6A218328
• Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 870", based on the 5-celled von Neumann neighborhood.at n=7A273704
• Solution of the complementary equation a(n) = 2*a(n-1) - a(n-2) + b(n-1), where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.at n=44A294866
• Numbers such that the product of their digits is equal to 10 times the sum of their prime factors, without multiplicity.at n=6A306313
• a(n) = A069359(A276086(n)), where A276086 is the primorial base exp-function and A069359(n) = n * Sum_{p|n} 1/p.at n=53A329029
• Number of ways to partition the set of vertices of a convex {n+8}-gon into 3 non-intersecting polygons.at n=18A350116
• a(n) = A069359(A276076(n)).at n=47A351951
• a(n) is the number of ways to place n indistinguishable balls into n distinguishable boxes with at least 4 boxes remaining empty.at n=8A370197