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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A272538 Call n/m a superdivisor of n if n/m + n divides (n/m)^(n/m) + n, (n/m)^n + n/m and n^(n/m) + n/m. This sequence gives the smallest number with n superdivisors. 2
2, 1, 406, 2926, 81810, 521626, 4276350, 1590715126, 266048146 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..8.

EXAMPLE

a(0) = 2 because 2/1 + 2 does not divide (2/1)^(2/1) + 2, (2/1)^2 + 2/1, 2^(2/1) + 2/1 and 2/2 + 2 does not divide (2/2)^(2/2) + 2, (2/2)^2 + 2/2, 2^(2/2) + 2/2: 4 does not divide 6, 6, 6 and 3 does not divide 3, 2, 3.

a(0) = 2 with superdivisors {}.

a(1) = 1 with superdivisor {1}.

a(2) = 406 with superdivisors {29, 203}.

a(3) = 2926 with superdivisors {77, 209, 1463}.

a(4) = 81810 with superdivisors {405, 909, 2727, 13635}.

a(5) = 521626 with superdivisors {4921, 7049, 13727, 37259, 260813}.

a(6) = 4276350 with superdivisors {2925, 16575, 54825, 237575, 427635, 712725}.

a(7) = 1590715126 with superdivisors {607607, 939029, 4253249, 10329319, 61181351, 113622509, 795357563}.

a(8) = 266048146 with superdivisors {538559, 655291, 1000181, 1461803, 2714777, 10232621, 19003439, 133024073}.

PROG

(PARI) superdivisors(n)=select(d->Mod(d, d+n)^d==-n && Mod(d, d+n)^n==-d && Mod(n, d+n)^d==-d, divisors(n))

a(n)=my(k); while(#superdivisors(k++)!=n, ); k \\ Charles R Greathouse IV, May 06 2016

CROSSREFS

Cf. A247477, A254748.

Sequence in context: A261437 A012867 A178393 * A087037 A354913 A036109

Adjacent sequences: A272535 A272536 A272537 * A272539 A272540 A272541

KEYWORD

nonn,more

AUTHOR

Juri-Stepan Gerasimov, Jan 19 2015

EXTENSIONS

a(4)-a(6) from Charles R Greathouse IV, Feb 19 2015.

Edited by Charles R Greathouse IV, May 06 2016

a(7)-a(8) from Charles R Greathouse IV, May 23 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 05:56 EST 2022. Contains 358512 sequences. (Running on oeis4.)