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!)
A230541 Numbers n such that the digits of sigma(n) are a permutation of those of sigma*(n), where sigma*(n) is the sum of anti-divisors of n (A066417). 1
11, 20, 22, 26, 33, 65, 82, 117, 209, 218, 376, 417, 483, 508, 537, 561, 675, 758, 910, 1186, 1208, 1317, 1350, 1828, 2039, 2192, 2347, 2471, 2840, 2889, 4129, 4369, 4389, 4495, 4893, 5007, 6430, 7276, 7690, 8246, 8777, 9289, 10651, 11727, 11797, 12048, 12099 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..100

EXAMPLE

Divisors of 376 are 1, 2, 4, 8, 47, 94, 376, 188 and sigma(376) = 720; anti-divisors of 376 are 3, 16, 251 and sigma*(376) = 270.

Therefore 376 is part of the sequence because the digits of 720 are a permutation of the digits of 270.

MAPLE

with(numtheory); P:= proc(i) local a, b, c, j, k, n, ok, p;

for n from 3 to i do b:=[]; c:=[];

k:=0; j:=n; while j mod 2<>1 do k:=k+1; j:=j/2; od;

a:=sigma(2*n+1)+sigma(2*n-1)+sigma(n/2^k)*2^(k+1)-6*n-2;

while a>0 do b:=[op(b), a mod 10]; a:=trunc(a/10); od; a:=sigma(n);

while a>0 do c:=[op(c), a mod 10]; a:=trunc(a/10); od;

if nops(b)=nops(c) then b:=sort(b); c:=sort(c); b:=b-c; ok:=1;

for j from 1 to nops(b) do if b[j]<>0  then ok:=0; break; fi; od;

if ok=1 then print(n); fi; fi; od; end; P(10^6);

CROSSREFS

Cf. A000203, A066417, A115920.

Sequence in context: A124250 A124251 A279431 * A053715 A250203 A339307

Adjacent sequences:  A230538 A230539 A230540 * A230542 A230543 A230544

KEYWORD

nonn,base,less

AUTHOR

Paolo P. Lava, Oct 23 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 March 2 06:30 EST 2021. Contains 341743 sequences. (Running on oeis4.)