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!)
A240968 Unitary anti-perfect numbers. 0
5, 8, 10, 41, 206, 1066, 2412, 3281, 8086, 11570, 29525, 57012, 73728, 410390, 413486, 775130, 2391485, 2454146, 2937446, 64563520, 100531166, 152032126, 988747406 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For any number x we consider the sum of its anti-divisors which are coprime to x (unitary anti-divisors). The sequence list the numbers for which this sum is equal to x.

Subset of A192270.

I found only 2 unitary anti-amicable numbers: 18208, 20470.

No other terms < 2147000000. Jud McCranie, Sep 21 2019.

LINKS

Table of n, a(n) for n=1..23.

EXAMPLE

Anti-divisors of 1066 are 3, 4, 9, 27, 52, 79, 164, 237, 711. The anti-divisors which are coprime to 1066 are 3, 9, 27, 79, 237, 711 and their sum is 3 + 9 + 27 + 79 + 237 + 711 = 1066.

MAPLE

P:=proc(q) local a, k, n;

for n from 3 to q do a:=0; b:=0;

for k from 2 to n-1 do if abs((n mod k)-k/2)<1 then

  if gcd(n, k)=1 then a:=a+k; fi; fi; od;

if n=a then print(n); fi; od; end: P(10^6);

CROSSREFS

Cf. A066272, A066417, A073930, A192270, A240979.

Sequence in context: A185001 A057154 A072524 * A187878 A191233 A314386

Adjacent sequences:  A240965 A240966 A240967 * A240969 A240970 A240971

KEYWORD

nonn,more

AUTHOR

Paolo P. Lava, Aug 05 2014

EXTENSIONS

a(14)-a(23) by Jud McCranie, Sep 21 2019.

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 January 27 13:45 EST 2022. Contains 350607 sequences. (Running on oeis4.)