login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072379 Sum_{k<=n} (sigma(k)^2), where sigma(k) denotes the sum of the divisors of k A000203. 9

%I #15 Feb 05 2019 04:55:05

%S 1,10,26,75,111,255,319,544,713,1037,1181,1965,2161,2737,3313,4274,

%T 4598,6119,6519,8283,9307,10603,11179,14779,15740,17504,19104,22240,

%U 23140,28324,29348,33317,35621,38537,40841,49122,50566,54166,57302

%N Sum_{k<=n} (sigma(k)^2), where sigma(k) denotes the sum of the divisors of k A000203.

%H Vaclav Kotesovec, <a href="/A072379/b072379.txt">Table of n, a(n) for n = 1..10000</a>

%F Ramanujan's asymptotic formula: (5/6)*Zeta(3)*n^3+O(n^2*log(n)^2)

%t Accumulate[Table[DivisorSigma[1, k]^2, {k, 1, 50}]] (* _Vaclav Kotesovec_, Sep 10 2018 *)

%o (PARI) a(n) = sum(k=1, n, sigma(k)^2) \\ _Michel Marcus_, Jun 20 2013

%Y Cf. A000203, A024916, A072861.

%Y Cf. A057434, A061502, A074789.

%K nonn

%O 1,2

%A Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jul 20 2002

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)