26326

Appears in sequences

• Expansion of (1-x)/(1-x+2*x^2+x^3).at n=22A078021
• Third row of Pascal-(1,2,1) array A081577.at n=18A081583
• a(n) = n! * Sum_{i,j,k,l >= 0, i+j+k+l = n} 1/(i!*j!*k!*l!).at n=9A092429
• Semiprimes in A054567.at n=26A113692
• Composite numbers k such that phi(x) = psi(k)*phi(k) has no solution.at n=23A292714
• a(n) = Sum_{k=1..n} phi(k)*phi(k+1)*phi(k+2), where phi(k) = A000010(k) is Euler's totient function.at n=25A335131
• Number of partitions of n containing a prime number of distinct primes and an arbitrary number of nonprimes.at n=40A344715