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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A246487 Numbers x such that sigma(x) + sigma(R(x)) = sigma(x + R(x)), where R(x) is the digit reversal of x and sigma(x) is the sum of the divisors of x. 1
78, 87, 104, 401, 1144, 2072, 2178, 2702, 4411, 7038, 7348, 7878, 8307, 8437, 8712, 8787, 11144, 11544, 12584, 15834, 20710, 20913, 21476, 21978, 22164, 26070, 31902, 43851, 44111, 44511, 46122, 48521, 66649, 67412, 87912, 94666, 102786, 122584, 122784, 126984 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
x = 15834 -> R(x) = 43851 and sigma(15834) + sigma(43851) = 40320 + 59904 = 100224 = sigma(15834 + 43851)= sigma(59685).
MAPLE
with(numtheory): P:=proc(q) local a, b, k, n;
for n from 1 to q do a:=n; b:=0;
for k from 1 to ilog10(n)+1 do b:=10*b+(a mod 10); a:=trunc(a/10);
od; if sigma(n)+sigma(b)=sigma(n+b) then print(n); fi;
od; end: P(10^6);
MATHEMATICA
Select[Range[130000], DivisorSigma[1, #]+DivisorSigma[1, IntegerReverse[#]] == DivisorSigma[1, #+IntegerReverse[#]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 27 2017 *)
PROG
(PARI) isok(n) = rn = subst(Polrev(digits(n)), x, 10); sigma(n + rn) == sigma(n) + sigma(rn); \\ Michel Marcus, Aug 29 2014
CROSSREFS
Sequence in context: A345476 A217006 A053083 * A039435 A043258 A044038
KEYWORD
nonn,base,easy
AUTHOR
Paolo P. Lava, Aug 27 2014
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 22 15:30 EST 2024. Contains 370256 sequences. (Running on oeis4.)