183648021599domain: NAppears in sequencesa(n) = 6*a(n-1) - a(n-2) + 2 with a(0) = 0, a(1) = 3.at n=15A001652Related to Pythagorean triples: alternate terms of A001652 and A046090.at n=15A046727Pell oblongs.at n=15A084159Pairs of integers (a,b) such a^2 + (a+1)^2 = b^2.at n=30A261116