22419

Appears in sequences

• a(n) = Sum_{k=1..n-1} k*sigma(k)*sigma(n-k).at n=17A000441
• y values corresponding to the x values in A023677.at n=62A023678
• Denominators of continued fraction convergents to sqrt(103).at n=11A041185
• Denominators of continued fraction convergents to sqrt(412).at n=9A041783
• Write fundamental unit for real quadratic field of discriminant n as x + y*omega; sequence gives values of y for n == 3 mod 4.at n=21A053375
• a(n) is smallest natural number a satisfying Pell equation b^2- d(n)*a^2= +1 or = -1, with d(n)=A000037(n) (nonsquare). Corresponding smallest b(n)=A077232(n).at n=92A077233
• Let p = n-th prime, take smallest solution (x,y) to the Pellian equation x^2 - p*y^2 = 1 with x and y >= 1; sequence gives value of y.at n=26A081234
• Let p = n-th prime of the form 4k+3, take the solution (x,y) to the Pellian equation x^2 - p*y^2 = 1 with x and smallest y >= 1; sequence gives value of y.at n=13A082394
• Antidiagonally reading the array, formed via: first, writing the primes in the first row (row_1), and forming all successive rows' elements using the previous rows' elements as: row_2(j) = row_1(j)*row_1(j+1) - row_1(j) - row_1(j+1), and so on. The first 'column' of the array, 2 1 -1 -1 -1 -1 -1 -1 ... is converted to its absolute value.at n=25A165401
• Sums of Pythagorean sextuples in increasing order: The sums of sets of six natural numbers which correspond to the lengths of the edges of a tetrahedron whose four faces are all different Pythagorean triangles.at n=39A248548
• The positive odd fundamental solutions y = y0(n) for the Pell equation x^2 - d*y^2 = +1. It turns out that d = d(n) coincides with A007970(n).at n=30A262026
• Numbers that yield a prime when prime(k+2) is inserted after the k-th digit (or prime(1) = 2 before the 1st digit for k=0), for 0 <= k <= number of digits.at n=11A304243
• a(n) = a(n-3) + a(n-2) + gcd(a(n-2), a(n-1)) with a(1) = a(2) = a(3) = 1.at n=33A370202