A300796 - OEIS

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

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 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A300796

Numbers x whose 10's complements y have the same sum of divisors of x, with x <> y.

3762, 4125, 4865, 5135, 5875, 6238, 37620, 41250, 42825, 44571, 48650, 48839, 49496, 50504, 51161, 51350, 55429, 57175, 58750, 62380, 376200, 389232, 397584, 399441, 412500, 417864, 428250, 434355, 436185, 445710, 446369, 472535, 481325, 483662, 483792, 486500

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Many patterns can be found, e.g. 3762*10^j, 4125*10^j, 4865*10^j, 5135*10^j, 5875*10^j, 6238*10^j, etc.

LINKS

Table of n, a(n) for n=1..36.

EXAMPLE

3762 is in the sequence because sigma(3762) = sigma(10^4-3762) = 9360.

5875 is in the sequence because sigma(5875) = sigma(10^4-5875) = 7488.

MAPLE

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

for n from 1 to q do a:=10^(ilog10(n)+1)-n;

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

MATHEMATICA

c10Q[n_]:=Module[{c=10^IntegerLength[n]-n}, c!=n&&DivisorSigma[1, n] == DivisorSigma[1, c]]; Select[Range[500000], c10Q] (* Harvey P. Dale, Sep 24 2021 *)

CROSSREFS

Cf. A000203, A055120, A300447.

Sequence in context: A133970 A252564 A137790 * A338545 A284079 A108179

Adjacent sequences: A300793 A300794 A300795 * A300797 A300798 A300799

KEYWORD

nonn,base,easy

AUTHOR

Paolo P. Lava, Mar 13 2018

STATUS

approved