cp's OEIS Frontend

A080716 Numbers n such that sum of the divisors of n equals the sum of the reversals of the divisors of n.

%I A080716 #17 Sep 07 2020 13:25:27
%S A080716 1,2,3,4,5,6,7,8,9,11,22,30,33,42,44,55,66,77,88,99,101,121,131,151,
%T A080716 181,191,202,242,262,303,313,330,353,363,373,383,393,404,462,484,505,
%U A080716 606,626,681,707,727,757,772,787,797,808,824,890,909,919,929,939,989,1111
%N A080716 Numbers n such that sum of the divisors of n equals the sum of the reversals of the divisors of n.
%H A080716 Amiram Eldar, <a href="/A080716/b080716.txt">Table of n, a(n) for n = 1..8811</a> (terms below 10^10, terms 1..300 from Paolo P. Lava)
%e A080716 Sum of divisors of 30: 1+2+3+5+6+10+15+30=72; sum of reversals of divisors of 30: 1+2+3+5+6+1+51+3=72. Therefore 30 belongs to the sequence.
%p A080716 isA080716 := proc(n)
%p A080716     simplify(A069192(n) = numtheory[sigma](n)) ;
%p A080716 end proc:
%p A080716 for n from 1 to 1000 do
%p A080716     if isA080716(n) then
%p A080716         printf("%d,",n) ;
%p A080716     end if;
%p A080716 end do: # _R. J. Mathar_, Sep 09 2015
%t A080716 rev[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[10^4], Apply[Plus, Map[rev, Divisors[ # ]]] == DivisorSigma[1, # ] &]
%t A080716 Select[Range[1200],Total[IntegerReverse/@Divisors[#]]==DivisorSigma[1,#]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Sep 07 2020 *)
%Y A080716 Cf. A000203, A069192, A069942.
%K A080716 base,nonn
%O A080716 1,2
%A A080716 _Joseph L. Pe_, Mar 05 2003