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a(n) = tau(7*n) = A000005(7*n).
10

%I #6 May 13 2024 12:21:57

%S 2,4,4,6,4,8,3,8,6,8,4,12,4,6,8,10,4,12,4,12,6,8,4,16,6,8,8,9,4,16,4,

%T 12,8,8,6,18,4,8,8,16,4,12,4,12,12,8,4,20,4,12,8,12,4,16,8,12,8,8,4,

%U 24,4,8,9,14,8,16,4,12,8,12,4,24,4,8,12,12,6,16,4

%N a(n) = tau(7*n) = A000005(7*n).

%H Vaclav Kotesovec, <a href="/A372787/a372787.jpg">Graph - the asymptotic ratio (100000 terms)</a>

%F Sum_{k=1..n} a(k) ~ (13*n*(log(n) + 2*gamma - 1) + n*log(7)) / 7, where gamma is the Euler-Mascheroni constant A001620.

%t Table[DivisorSigma[0, 7*n], {n, 1, 150}]

%Y Cf. A283078.

%Y Cf. A000005, A099777, A372713, A372784, A372785, A372786, A372788, A372789, A372790, A372791, A372792.

%K nonn

%O 1,1

%A _Vaclav Kotesovec_, May 13 2024