[go: up one dir, main page]

login
A080716
Numbers n such that sum of the divisors of n equals the sum of the reversals of the divisors of n.
2
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 30, 33, 42, 44, 55, 66, 77, 88, 99, 101, 121, 131, 151, 181, 191, 202, 242, 262, 303, 313, 330, 353, 363, 373, 383, 393, 404, 462, 484, 505, 606, 626, 681, 707, 727, 757, 772, 787, 797, 808, 824, 890, 909, 919, 929, 939, 989, 1111
OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..8811 (terms below 10^10, terms 1..300 from Paolo P. Lava)
EXAMPLE
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.
MAPLE
isA080716 := proc(n)
simplify(A069192(n) = numtheory[sigma](n)) ;
end proc:
for n from 1 to 1000 do
if isA080716(n) then
printf("%d, ", n) ;
end if;
end do: # R. J. Mathar, Sep 09 2015
MATHEMATICA
rev[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[10^4], Apply[Plus, Map[rev, Divisors[ # ]]] == DivisorSigma[1, # ] &]
Select[Range[1200], Total[IntegerReverse/@Divisors[#]]==DivisorSigma[1, #]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 07 2020 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Joseph L. Pe, Mar 05 2003
STATUS
approved