A300796 - OEIS

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

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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