18270

Appears in sequences

• Number of permutations of [n] with exactly 2 increasing runs of length at least 2.at n=4A000363
• Triangle read by rows: T(n,k) is the number of permutations of [n] with k increasing runs of length at least 2.at n=22A008971
• Expansion of e.g.f.: sech(arctanh(x)+log(x+1))=1-4/2!*x^2+6/3!*x^3+45/4!*x^4-300/5!*x^5...at n=7A013166
• XOR-convolution of squares A000290 with themselves.at n=29A033460
• a(n) = 3*(n - 2)*(5*n -11).at n=35A060785
• Numbers k such that sigma(k) = phi((prime(k)+prime(k+1))/2).at n=10A068365
• Integers k such that omega(k) = omega(k-1) + omega(k-2) + omega(k-3), where omega(n) is the number of distinct prime factors of n.at n=11A076252
• Integers that are Rhonda numbers to more than one base.at n=36A100988
• Numbers k such that the central binomial coefficient C(2k,k) is divisible by k^2.at n=31A121943
• Triangle read by rows: T(n,k) is number of hex trees with n edges and k nonroot nodes of outdegree 2.at n=35A126183
• Row sums of triangle A134480.at n=27A134481
• Subset of A020342 (vampire numbers, definition 1) listing numbers which have more than one such representation of the desired form.at n=11A144563
• Weight distribution of [63,51,5] primitive binary BCH code.at n=6A151773
• Triangle of polynomial coefficients related to the o.g.f.s. of the RBS1 polynomials.at n=12A160486
• Integers n such that the century defined by the interval [100n+1, 100n+100] (i.e., the (n+1)-st century) contains exactly one Ormiston prime pair and no other primes.at n=1A162895
• Numbers such that each digit from 0 to 9 appears at least 7 times in the digits of their divisors.at n=16A175507
• Numbers with prime factorization pqrst^2.at n=32A189983
• Triangle of coefficients arising in expansion of n-th derivative of tan(x) + sec(x).at n=40A198895
• Irregular triangular array read by rows T(n,k) is the number of 2-colored labeled graphs that have exactly k edges, n >= 2, 0 <= k <= A033638(n).at n=35A201143
• Denominator of the complexity index B of the path graph on n vertices (n>=2).at n=7A206485