27193

Appears in sequences

• Pisot sequence E(5,21), a(n) = floor( a(n-1)^2/a(n-2) + 1/2 ).at n=6A010917
• G.f.: (1+x)/Product_{m>0} (1 - x^m).at n=35A084376
• Numbers k such that sigma(phi(k)) - phi(sigma(k)) is nonzero and divisible by sigma(k), that is A065395(k)/A000203(k) is a nonzero integer.at n=26A092588
• Greatest multiple of the n-th prime in A098962.at n=19A099620
• Numbers with d digits (d>0) which have at least 2d distinct primes as substrings.at n=30A168167
• Numbers missing from A001033 despite satisfying the necessary congruence conditions (see comments).at n=38A274470
• G.f. A(x) satisfies: A(x) = x * (1 + A(x))^4 / (1 - 4 * A(x)).at n=5A366016
• a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(n+k,k) * binomial(n*(n+1),n-k) * n^k.at n=4A366038