21253

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 95.at n=15A020434
• Greatest number having exactly n representations as ab+ac+bc with 0 < a < b < c.at n=16A094377
• Semiprimes in A056108.at n=25A113527
• Numbers n such that primorial(n)/2 + 8 is prime.at n=26A139441
• Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 1101-1111 pattern in any orientation.at n=9A146870
• a(n) = n^2 + 731*n + 1.at n=28A180919
• Sum of the largest parts in the partitions of 3n into 3 parts.at n=24A236370
• Sum of the largest parts in the partitions of 4n into 4 parts with smallest part = 1.at n=18A240711
• Numbers k such that 7*10^k - 69 is prime.at n=23A281643
• a(n) is the least integer k such that k/Fibonacci(n) > Pi.at n=20A293678
• a(n) is the integer k that minimizes |k/Fibonacci(n) - Pi|.at n=20A293679
• Expansion of Product_{k>=1} (1 + (x*(1 - x))^k).at n=29A307501
• Composite hypotenuses of primitive Pythagorean triangles (A120961) that are not circumdiameters of non-Pythagorean primitive Heronian triangles (A285579).at n=29A329148
• Numerators of coefficients associated with the second virial coefficient for rigid spheres with imbedded point dipoles.at n=10A336061
• Numbers that are the sum of eight fourth powers in exactly eight ways.at n=30A345840
• Numbers j in pairs (j,k), with j <> k +- 1, such that the sum of their cubes is equal to a centered cube number.at n=50A352135
• Composite numbers in A381019 which are immediately followed by another composite number, in order of their appearance.at n=22A379810
• Expansion of 1/sqrt((1-x^3)^2 - 4*x^4).at n=27A383571