19795

Appears in sequences

• Partial sum of usigma is divisible by n, where usigma(n) = A034448(n) and summatory-usigma(n) = A064609(n).at n=10A064611
• A Wallis pair (x,y) satisfies sigma(x^2) = sigma(y^2); sequence gives y's for indecomposable Wallis pairs with x < y (ordered by values of x).at n=38A075769
• Group the natural numbers such that the n-th group sum is divisible by prime(n): (1, 2, 3), (4, 5), (6, 7, 8, 9), (10, 11), (12, 13, 14, 15, 16, 17, 18, 19, 20, 21), ... Sequence contains the sum of the terms in the n-th group.at n=27A086491
• a(n) = 2*A090495(n) - 1.at n=38A274297
• G.f. A(x) satisfies A(x) = 1 / ((1 - x) * (1 - 2 * x * A(x)^2)).at n=5A349253