OFFSET
1,2
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
EXAMPLE
a(12)=14 because 14 and reverse of 14, i.e., 41, are deficient numbers.
a(13)=15 because 15 is a deficient number which on reversing its digits also gives a deficient number, i.e., 51.
MATHEMATICA
Select[Range@106, DivisorSigma[1, #] < 2 # && DivisorSigma[1, n = FromDigits@Reverse@IntegerDigits@#] < 2 n &] (* Ivan Neretin, Dec 19 2015 *)
PROG
(PARI) isdefic(n) = (sigma(n) < 2*n);
isok(n) = isdefic(n) && isdefic(eval(concat(Vecrev(Str(n))))); \\ Michel Marcus, Dec 20 2015
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, Jun 11 2007
STATUS
approved