

A098770


Abundant numbers whose reversal is a deficient number.


3



12, 18, 20, 30, 36, 40, 54, 56, 70, 72, 78, 80, 90, 96, 100, 102, 104, 108, 112, 114, 120, 126, 132, 138, 140, 144, 150, 156, 160, 162, 168, 174, 176, 180, 186, 192, 196, 198, 200, 208, 220, 224, 260, 280, 300, 304, 306, 308, 312, 318, 320, 324, 330, 336, 340
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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

Cf. A004086, A005100, A005101, A098768.
Sequence in context: A340780 A054753 A098899 * A333928 A181487 A091191
Adjacent sequences: A098767 A098768 A098769 * A098771 A098772 A098773


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



