6970150domain: NAppears in sequencesa(n) = (3*n+4)*binomial(n+7, 7)/4.at n=18A054487Area ar/6 (divided by 6) of primitive Pythagorean triangles such that perimeters are Averages of twin prime pairs, q=p+1, a=q^2-p^2, c=q^2+p^2, b=2*p*q, ar=a*b/2; s=a+b+c, s-+1 are primes.at n=23A155177