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A028985
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Nonsquare palindromes whose sum of divisors is odd.
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1
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2, 8, 242, 20402, 24642, 2004002, 2138312, 2468642, 85099058, 200040002, 204060402, 242484242, 291080192, 20000400002, 20442824402, 24204840242, 29956665992, 88484148488, 297738837792, 2000004000002, 2004006004002, 2040608060402, 2420048400242
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OFFSET
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1,1
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COMMENTS
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Palindromes of the form 2*k^2, with k a nonzero integer. - Stéphane Rézel, Jan 04 2018
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LINKS
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Stéphane Rézel, Table of n, a(n) for n = 1..68
Proof Wiki, Sigma_Function_Odd_iff_Argument_is_Square_or_Twice_Square
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MATHEMATICA
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Select[Array[2 #^2 &, 10^7], PalindromeQ] (* Michael De Vlieger, Jan 10 2018 *)
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PROG
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(PARI) for(n=1, 10^9, my(d=digits(2*n^2)); if(d==Vecrev(d), print1(2*n^2, ", "))); \\ Joerg Arndt, Jan 10 2018
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CROSSREFS
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Sequence in context: A091503 A009588 A125264 * A067583 A120378 A012345
Adjacent sequences: A028982 A028983 A028984 * A028986 A028987 A028988
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest
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EXTENSIONS
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Offset corrected and a(14)-a(21) from Donovan Johnson, Apr 25 2010
a(22)-a(23) from Donovan Johnson, Jun 16 2011
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STATUS
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approved
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