15513960domain: NAppears in sequencesNumbers that can be expressed as the difference of the squares of primes in exactly twenty-two distinct ways.at n=17A092018Sequences from the quartic oscillator.at n=21A228406a(n) = Sum_{k=0..floor(n/4)} binomial(n,k) * binomial(2*k,n-4*k).at n=25A389126