21582

Appears in sequences

• Values of y in solutions (x,y,z) to the Diophantine equation x^3-x^2+y^3-y^2=z^3-z^2, with 1<x<y<z arranged in order of increasing x.at n=32A138668
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, -1), (-1, -1, 0), (-1, 0, 1), (1, 0, 1), (1, 1, -1)}.at n=9A148889
• Numbers k such that Sum_{d|k} sigma(d)^3/d is an integer, where d are the divisors of k.at n=9A226566
• a(n) = floor(M(g(n-1)+1, ..., g(n))), where M = harmonic mean and g(n) = n^3 + n^2 + n + 1.at n=27A227015
• a(n) = 2^n * Sum_{k=0..n} k^p*q^k, where p=3, q=-1/2.at n=18A232604
• Number x such that sigma(x) = usigma(x) + (-1)sigma(x), where sigma(x) is the sum of divisors of x (A000203), usigma(x) is the sum of unitary divisors of x (A034448) and (-1)sigma(x) is defined in A049060.at n=4A258106
• Triples of practical numbers: numbers n such that n-2, n, n+2 are all practical numbers.at n=24A287682
• Number of 5-cycles in the n-polygon diagonal intersection graph.at n=30A300553
• a(0) = 1; a(n) = Sum_{k=1..n} -lambda(k+1)*a(n-k), where lambda() is the Liouville function (A008836).at n=26A307240
• a(n) = Sum_{d|n} (n/d)^d * binomial(d+n,n).at n=7A363661