183251937963domain: NAppears in sequencesa(n) = (2^(2*n + 1) + 1)/3.at n=19A007583Nonprime numbers of the form 1 + Sum_{k=1..m} 2^(2*k - 1).at n=9A127959A trisection of A024495.at n=13A132805Fourth quadrisection of Jacobsthal numbers A001045: a(n)=16a(n-1)-5.at n=9A141060Interleave A007583 and A000012.at n=38A166752