This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A064840 #31 Sep 08 2022 08:45:04
%S A064840 1,6,8,21,12,48,16,60,39,72,24,168,28,96,96,155,36,234,40,252,128,144,
%T A064840 48,480,93,168,160,336,60,576,64,378,192,216,192,819,76,240,224,720,
%U A064840 84,768,88,504,468,288,96,1240,171,558,288,588,108,960,288,960,320,360
%N A064840 a(n) = tau(n)*sigma(n).
%C A064840 Dirichlet convolution of A034761 with (the Dirichlet inverse of A037213). - _R. J. Mathar_, Feb 11 2011
%H A064840 Indranil Ghosh, <a href="/A064840/b064840.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Harry J. Smith)
%H A064840 Vaclav Kotesovec, <a href="/A064840/a064840.jpg">Graph - the asymptotic ratio</a>
%F A064840 Multiplicative with a(p^e) = (p^(e+1)-1)*(e+1)/(p-1). a(n) = (1/2)*Sum_{i|n, j|n} (i+j).
%F A064840 Dirichlet g.f. (zeta(s)*zeta(s-1))^2/zeta(2s-1). - _R. J. Mathar_, Feb 11 2011
%F A064840 Sum_{k=1..n} a(k) ~ Pi^4 * n^2 / (144*Zeta(3)) * (2*log(n) - 1 + 4*gamma - 4*Zeta'(3)/Zeta(3) + 24*Zeta'(2)/Pi^2), where gamma is the Euler-Mascheroni constant A001620. - _Vaclav Kotesovec_, Jan 31 2019
%e A064840 For n = 10, a(10) = sigma(10) * tau(10) = 18 * 4 = 72. - _Indranil Ghosh_, Jan 20 2017
%p A064840 with(numtheory): seq(sigma(n)*tau(n), n=1..58) ; # _Zerinvary Lajos_, Jun 04 2008
%t A064840 Table[ DivisorSigma[0, n] * DivisorSigma[1, n], {n, 1, 58}] (* _Jean-François Alcover_, Mar 26 2013 *)
%o A064840 (Magma) [ NumberOfDivisors(n)*SumOfDivisors(n) : n in [1..40]];
%o A064840 (PARI) { for (n=1, 1000, a=numdiv(n)*sigma(n); write("b064840.txt", n, " ", a) ) } \\ _Harry J. Smith_, Sep 28 2009
%Y A064840 Cf. A000005, A000203, A007503, A062354, A062355.
%K A064840 mult,nonn
%O A064840 1,2
%A A064840 _Vladeta Jovovic_, Oct 25 2001