18690

Appears in sequences

• Numbers n such that s=n^2 gives prime quadruples (30s+11, 30s+13, 30s+17, 30s+19).at n=3A087772
• Record values in A106530.at n=18A106531
• Numbers k such that 2*k-1, 4*k-1, 6*k-1 and 8*k-1 are primes.at n=15A124487
• Irregular triangle read by rows T(n,k) (n>=1, 0<=k<=n(n-1)/2) giving the total number of connected components in all subgraphs (V,E') with |E'|=k of the complete labeled graph K_n=(V,E).at n=45A125205
• Records for unitary abundant numbers, i.e., those integers which set a record for having a greater unitary abundance than any of their predecessors.at n=41A129499
• The number of divisors d of n! such that d < A000793(n) (Landau's function g(n)) and the symmetric group S_n contains no elements of order d.at n=52A211391
• G.f. A(x) satisfies: the sum of the coefficients of x^k, k=0..n, in A(x)^n equals (3*n)!/n!^3, which is de Bruijn's sequence S(3,n) (A006480), for n>=0.at n=5A232683
• Triangle of coefficients of polynomials p_n(x) (exponents in increasing order) where 2^(x-n-1)p_n(x)/n! counts the ways a game of Nim with two piles of sizes x and n can be played out (x > 0, n >= 0).at n=42A289329
• Inverse matrix of A135494.at n=51A298673
• Numbers n for which 2 < A257993(A276086(A276086(n))) < A257993(n), where A276086 converts the primorial base expansion of n into its prime product form, and A257993 returns the index of the least prime not present in its argument.at n=12A328762
• Positions of 0's in A330314.at n=15A330325
• Number of maximal irredundant sets in the torus grid graph C_n square C_n.at n=2A347613
• a(n) = Sum_{k=0..floor((n-1)/3)} 2^k * |Stirling1(n,3*k+1)|.at n=8A357832
• Composite numbers with properties that its digits (which may appear with multiplicity) may not appear in any of its factors (wherein the digits may also appear with multiplicity) and the combined digits of the product and the factors must have at least one of each of the ten digits.at n=29A370972
• Triangle read by rows: T(n,k) is the number of nested cycle partitions of n labeled nodes into k components.at n=51A392471