20605

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 49.at n=26A020388
• Partial sums of usigma(n)^2: square of the sum of unitary divisors of n.at n=29A074789
• Third row of Pascal-(1,5,1) array A081580.at n=34A081589
• Numbers k such that k and k^2 use only the digits 0, 2, 4, 5 and 6.at n=50A136898
• Hypotenuse C 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, s=a+b+c, s-+1 are primes.at n=12A155175
• Positive numbers y such that y^2 is of the form x^2+(x+409)^2 with integer x.at n=8A160577
• Triangle read by rows: T(n,k) is the coefficient A_k in the transformation of 1 + x + x^2 + ... + x^n to the polynomial A_k*(x-3k)^k for 0 <= k <= n.at n=52A248978
• Numbers of the form p*q*r where p, q, r are distinct primes congruent to 1 mod 4 such that Legendre(p/q) = Legendre(p/r) = Legendre(q/r) = -1.at n=19A323271
• Centered square numbers which are sphenic numbers.at n=10A380882