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A072363 Composite numbers whose sum of divisors is palindromic. 2

%I #9 Aug 17 2020 02:05:36

%S 4,81,96,98,130,146,162,166,201,205,208,221,244,274,300,314,325,333,

%T 365,388,422,438,489,519,559,633,685,793,803,1376,1419,1505,1548,1806,

%U 1841,2021,2268,2284,2305,2561,2611,2666,2751,2763,2838,2881,2892,2967,3010

%N Composite numbers whose sum of divisors is palindromic.

%H Amiram Eldar, <a href="/A072363/b072363.txt">Table of n, a(n) for n = 1..10000</a>

%e a(2) = 81: sum of divisors of 81 = 1+3+9+27+81 = 121, which is a palindrome.

%t Select[Range[3000], CompositeQ[#] && PalindromeQ @ DivisorSigma[1, #] &] (* _Amiram Eldar_, Aug 17 2020 *)

%Y Cf. A000203, A002113, A072362.

%K base,nonn

%O 1,1

%A _Shyam Sunder Gupta_, Jul 18 2002

%E More terms from _Amiram Eldar_, Aug 17 2020

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)