163376domain: NAppears in sequencesa(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t = A000032 (Lucas numbers).at n=20A023861Numbers k such that k and k + 1 are both of the form p*q^4 where p and q are distinct primes.at n=18A215197