login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A270528 Sum of divisors of the products of the smaller and larger parts of the partitions of n into two parts. 1
0, 1, 3, 11, 19, 34, 58, 91, 120, 167, 245, 296, 413, 471, 574, 731, 948, 961, 1335, 1395, 1645, 1872, 2398, 2344, 2994, 3109, 3603, 3865, 4865, 4388, 5960, 5851, 6608, 7006, 8189, 7811, 10203, 9806, 11000, 11147, 13930, 12216, 16093, 15118, 16459, 17459 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..46.

Index entries for sequences related to partitions

FORMULA

a(n) = Sum_{i=1..floor(n/2)} sigma(i*(n-i)).

EXAMPLE

a(5) = 19; the partitions of 5 into two parts are (1,4) and (2,3). The sum of divisors of the products of the partitions is sigma(4) + sigma(6) = (1+2+4) + (1+2+3+6) = 7 + 12 = 19.

MAPLE

with(numtheory): A270528:=n->add(sigma(i*(n-i)), i=1..floor(n/2)): seq(A270528(n), n=1..100);

MATHEMATICA

Table[Sum[DivisorSigma[1, i*(n - i)], {i, Floor[n/2]}], {n, 80}]

PROG

(PARI) a(n) = sum(i=1, n\2, sigma(i*(n-i))); \\ Michel Marcus, Mar 18 2016

CROSSREFS

Cf. A000203, A253275.

Sequence in context: A014223 A023265 A018557 * A213540 A085616 A138723

Adjacent sequences:  A270525 A270526 A270527 * A270529 A270530 A270531

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Mar 18 2016

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 May 24 06:53 EDT 2019. Contains 323529 sequences. (Running on oeis4.)