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Numbers n such that greatest prime dividing n = greatest prime dividing R(n), where R(n) is the digit reversal of n and n is a nonpalindromic number.
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%I #12 Jan 30 2017 11:22:37

%S 18,27,50,70,72,81,110,132,198,220,231,264,297,330,396,440,462,495,

%T 500,528,540,550,594,660,693,700,770,792,825,880,891,990,1010,1066,

%U 1089,1100,1107,1110,1210,1212,1310,1313,1320,1332,1410,1414,1443,1452,1510,1515,1572,1584,1610,1616,1665,1692,1710,1717,1810,1818,1910,1919,1980,1998

%N Numbers n such that greatest prime dividing n = greatest prime dividing R(n), where R(n) is the digit reversal of n and n is a nonpalindromic number.

%C Numbers n such that A006530(n) = A006530(A004086(n)) and A136522(n) = 0.

%H Indranil Ghosh, <a href="/A279108/b279108.txt">Table of n, a(n) for n = 1..2337</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GreatestPrimeFactor.html">Greatest Prime Factor</a>

%e 18 is in the sequence because 18 is a nonpalindromic number, 18 = 2*3^2, 81 = 3^4 and gpf(18) = gpf(81) = 3.

%t Select[Range[2000], FactorInteger[#][[-1, 1]] == FactorInteger[FromDigits[Reverse[IntegerDigits[#]]]][[-1, 1]] && !PalindromeQ[#] & ]

%Y Cf. A004086, A006530, A136522.

%K nonn,base

%O 1,1

%A _Ilya Gutkovskiy_, Dec 06 2016