18669

Appears in sequences

• Divisors of 2^42 - 1.at n=35A003547
• Expansion of 1/((1-x)(1-4x)(1-6x)(1-7x)).at n=4A021804
• Numbers k that divide 5^k + 4^k.at n=34A045590
• Integers k such that phi(prime(k)+1) = phi(prime(k)-1).at n=11A066902
• Matrix product of Stirling1-triangle A008275(n,k) and unsigned Lah-triangle |A008297(n,k)|.at n=40A079639
• Number of rules of a context-free grammar in Chomsky normal form that generates all permutations of n symbols.at n=8A090326
• Number of nonisomorphic partitions of n on the Ferrers diagram.at n=40A095814
• a(n) = 1 + (1200 + (634 + (225 + (85 + (15 + n)*n)*n)*n)*n)*n/720.at n=13A145128
• a(n) = A154798(n)/2.at n=8A163288
• A symmetrical triangle sequence:q=3;c(n,q)=Product[1 - q^i, {i, 1, n}];t(n,m,q)=-Eulerian[n + 1, m] + 2*c(n, q)/(c(m, q)*c(n - m, q)).at n=46A176428
• Number of (w,x,y,z) with all terms in {1,...,n} and w<2x and y<=3z.at n=13A212509
• Numbers k such that 2*k is a partition number.at n=16A213179
• Partial sums of the second power of arithmetic derivative function A003415.at n=36A231864
• Table where row n lists numbers N equal to the determinant of an n X n circulant having as a row the base n+1 digits of N.at n=43A303262
• Numbers k such that sopfr(k) = tau(k)^2.at n=14A305026
• "Primitive" numbers k such that k divides 4^k - 1.at n=18A323203
• Number of connected graphs, where vertices are labeled with positive integers summing to n, and where identically labeled vertices are indistinguishable and cannot be connected with an edge.at n=13A337717
• Column 4 of table A390148.at n=36A390465
• a(n) = Sum_{k=0..floor(2*n/7)} binomial(3*k,2*n-7*k).at n=24A392436