221001domain: NAppears in sequencesa(n) = n^2 written in base 3.at n=26A001738E.g.f.: A(x) = exp(x*A(x)^4*exp(x^2*A(x)^8*exp(x^3*A(x)^12*exp(x^4*A(x)^16*exp(...))))), an infinite power tower.at n=5A141359Pseudoprimes to base 6, written in base 6.at n=37A26210311-gonal numbers which are products of four distinct primes.at n=27A354086