OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 18 because 18 is the second abundant number which on reversing its digits gives a deficient number, namely 81.
MATHEMATICA
rev[n_] := FromDigits @ Reverse @ IntegerDigits[n]; Select[Range[340], DivisorSigma[1, #] > 2*# && DivisorSigma[1, (r = rev[#])] < 2*r &] (* Amiram Eldar, Aug 26 2020 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Shyam Sunder Gupta, Oct 02 2004
EXTENSIONS
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 21 2007
STATUS
approved