A333844 - OEIS

A333844

G.f.: Sum_{k>=1} k * x^(k^4) / (1 - x^(k^4)).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3

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OFFSET

1,16

COMMENTS

Sum of 4th roots of 4th powers dividing n.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

A. Dixit, B. Maji, and A. Vatwani, Voronoi summation formula for the generalized divisor function sigma_z^k(n), arXiv:2303.09937 [math.NT], 2023, sigma(z=1,k=4,n).

FORMULA

Dirichlet g.f.: zeta(s) * zeta(4*s-1).

If n = Product (p_j^k_j) then a(n) = Product ((p_j^(floor(k_j/4) + 1) - 1)/(p_j - 1)).

Sum_{k=1..n} a(k) ~ zeta(3)*n + zeta(1/2)*sqrt(n)/2. - Vaclav Kotesovec, Dec 01 2020

MATHEMATICA

nmax = 112; CoefficientList[Series[Sum[k x^(k^4)/(1 - x^(k^4)), {k, 1, Floor[nmax^(1/4)] + 1}], {x, 0, nmax}], x] // Rest

Table[DivisorSum[n, #^(1/4) &, IntegerQ[#^(1/4)] &], {n, 112}]

f[p_, e_] := (p^(Floor[e/4] + 1) - 1)/(p - 1); a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Dec 01 2020 *)

CROSSREFS

Cf. A000203, A053164, A063775, A069290, A300909, A333843.

Sequence in context: A103755 A355818 A326538 * A317933 A363329 A370079

Adjacent sequences: A333841 A333842 A333843 * A333845 A333846 A333847

KEYWORD

nonn,mult

AUTHOR

Ilya Gutkovskiy, Apr 07 2020

STATUS

approved