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!)
A336565 Numbers k for which (A057723(k)-k) is equal to gcd(k-A308135(k), A057723(k)-k). 4
6, 28, 234, 496, 588, 600, 1521, 1638, 6552, 8128, 55860, 89376, 33550336, 168836850 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers k for which A336563(k) = A336566(n) [= gcd(A336563(n), A336564(n))].

Numbers k such that either both A336563(k) and A336564(k) are zero (in which case k is squarefree), or A336563(k) divides A336564(k), in which case k is not squarefree.

Also numbers k for which A336647(n) = 2*n - A057723(n).

Question: Are there any other odd terms apart from 1521 = 39^2 ?

LINKS

Table of n, a(n) for n=1..14.

Index entries for sequences where odd perfect numbers must occur, if they exist at all

PROG

(PARI)

A007947(n) = factorback(factorint(n)[, 1]);

A057723(n) = { my(r=A007947(n)); (r*sigma(n/r)); };

isA336565(n) = { my(b=A057723(n), c=(sigma(n)-b), d=(b-n)); (gcd(d, (n-c))==d); };

CROSSREFS

Cf. A057723, A308135, A336563, A336564, A336566, A336647.

Cf. A000396 (a subsequence).

Cf. also A326145.

Sequence in context: A052395 A034660 A206708 * A216413 A090898 A134872

Adjacent sequences:  A336562 A336563 A336564 * A336566 A336567 A336568

KEYWORD

nonn,more

AUTHOR

Antti Karttunen, Jul 26 2020

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 April 18 09:06 EDT 2021. Contains 343087 sequences. (Running on oeis4.)