20943
domain: N
Appears in sequences
- Composite numbers k such that k!/k# - 1 is prime, where k# = primorial numbers A034386.at n=27A049421
- Numbers k such that k!/k#-1 is prime, where k# is the primorial function (A034386).at n=32A140293
- a(n) = 729*n - 198.at n=28A156772
- Partial sums of A211681.at n=15A213299
- Numbers x such that the sum of all their cyclic permutations is equal to that of all cyclic permutations of sigma(x) and all cyclic permutations of Euler totient function phi(x).at n=18A247317
- O.g.f.: exp( Sum_{n>=1} A256357(n^2)*x^n/n ), where exp( Sum_{n>=1} A256357(n)*x^n/n ) = 1 + Sum_{n>=1} x^(n^2) + x^(2*n^2).at n=27A258656
- Numbers m such that Sum_{d|m} (tau(d)/sigma(d)) is an integer h where tau(k) = the number of the divisors of k (A000005) and sigma(k) = the sum of the divisors of k (A000203).at n=6A323781