login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A227733 a(n) = sigma(2*n)^2 - sigma(n)^2. 2
8, 40, 128, 176, 288, 640, 512, 736, 1352, 1440, 1152, 2816, 1568, 2560, 4608, 3008, 2592, 6760, 3200, 6336, 8192, 5760, 4608, 11776, 7688, 7840, 12800, 11264, 7200, 23040, 8192, 12160, 18432, 12960, 18432, 29744, 11552, 16000, 25088, 26496, 14112, 40960, 15488, 25344, 48672, 23040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Here sigma(n) is the sum of divisors of n (A000203).

LINKS

Paul D. Hanna, Table of n, a(n) for n = 1..1000

FORMULA

Logarithmic derivative of A227732.

EXAMPLE

L.g.f.: L(x) = 8*x + 40*x^2/2 + 128*x^3/3 + 176*x^4/4 + 288*x^5/5 + 640*x^6/6 +...

where

exp(L(x)) = 1 + 8*x + 52*x^2 + 288*x^3 + 1396*x^4 + 6208*x^5 + 25744*x^6 +...+ A227732(n)*x^n +...

PROG

(PARI) {a(n)=sigma(2*n)^2-sigma(n)^2}

for(n=1, 50, print1(a(n), ", "))

CROSSREFS

Cf. A227732.

Sequence in context: A135796 A105374 A162668 * A191903 A028596 A264602

Adjacent sequences:  A227730 A227731 A227732 * A227734 A227735 A227736

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 24 2013

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 8 08:27 EDT 2020. Contains 336293 sequences. (Running on oeis4.)