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A227228 Palindromes greater than 10 whose sum of proper divisors is also a palindrome greater than 10. 1

%I #32 Oct 17 2014 05:27:12

%S 333,646,656,979,1001,3553,10801,11111,18581,31713,34943,48484,57375,

%T 95259,99099,158851,262262,569965,1173711,1216121,1399931,1439341,

%U 1502051,1925291,3203023,3436343,3659563,3662663,3803083,3888883,5185815,5352535,5893985

%N Palindromes greater than 10 whose sum of proper divisors is also a palindrome greater than 10.

%C The palindromic primes (A002385) (whose sum of proper divisors is 1) are not included in this sequence.

%H Donovan Johnson, <a href="/A227228/b227228.txt">Table of n, a(n) for n = 1..260</a> (terms < 10^14)

%e 10801 = 1543*7*1 and 1543 + 7 + 1 = 1551 (a palindrome). So, 10801 is a member of this sequence.

%o (Python)

%o from sympy import divisors

%o def rev(n):

%o ..r = ''

%o ..for i in str(n):

%o ....r = i + r

%o ..return int(r)

%o for i in range(10**6):

%o ..s = sum(divisors(i))-i

%o ..if rev(i) == i and s > 10 and rev(s) == s:

%o ....print(i,end=', ')

%o # simplified by _Derek Orr_, Oct 16 2014

%Y Cf. A002113, A001065, A002385.

%K nonn,base

%O 1,1

%A _Derek Orr_, Sep 19 2013

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Last modified May 7 20:13 EDT 2024. Contains 372317 sequences. (Running on oeis4.)