202500

Appears in sequences

• Denominator of sum of -4th powers of divisors of n.at n=29A017672
• a(n) = [ a(n-1)/a(1) ] + [ a(n-2)/a(2) ] + ... + [ a(1)/a(n-1) ], for n >= 3.at n=30A022876
• Numbers k such that k is a square and remains a square when its leading digit is increased by one.at n=4A067225
• Numbers k such that the numerator of Sum_{d|k} 1/d > 3*k.at n=14A069096
• Numbers k such that Sum_{d|k} d/core(d) > 2*k, where core(d) is the squarefree part of d.at n=35A069266
• Squares arising in A085039. n-th partial sum of A085039.at n=22A085040
• Numbers of the form 4k^4 or (kp)^p for prime p > 2 and k = 1, 2, 3, ....at n=35A097792
• a(n)=denominator of the probability that (x-y)/(x+y)+(y-z)/(y+z)+(z-u)/(z+u)+ (u-x)/(u+x) >0, assuming that each random quadruple of integers (x,y,z,u), with a<=x,y,z,u<=n, is equally likely.at n=29A106200
• Squares for which the sum of the digits, the product of the digits, the digital root and the multiplicative digital root are all squares.at n=28A117680
• Refactorable numbers k such that the number of odd divisors r is odd, the number of even divisors s is even and both r and s are divisors of k.at n=9A120349
• Even refactorable numbers k such that the number r of odd divisors is odd, the number s of even divisors is even, both r and s are divisors of k and k is the first number for which the triple (r,s,t) occurs, where t is the number of divisors of k.at n=7A120359
• a(n) = ceiling(n^4/4).at n=30A131478
• a(n) = floor(n^4/4).at n=30A131479
• a(n) = 4*n^4.at n=15A141046
• Squares s(n) such that cube(n)-square(n)-1 and cube(n)+square(n)+1 are primes.at n=17A155931
• Squares that remain squares when prefixed with a 4.at n=6A167038
• Squares that remains a square when some single digit is inserted in front of its decimal expansion.at n=27A167045
• 1/4 the number of n X 5 0..3 arrays with no element equal both to the element above and to the element to its left.at n=1A185563
• T(n,k)=1/4 the number of nXk 0..3 arrays with no element equal both to the element above and to the element to its left.at n=19A185567
• T(n,k)=1/4 the number of nXk 0..3 arrays with no element equal both to the element above and to the element to its left.at n=16A185567