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A115897
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Numbers k such that sigma(k) + phi(k) is a palindrome.
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5
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1, 2, 3, 4, 10, 11, 21, 49, 92, 101, 115, 131, 145, 186, 200, 201, 206, 207, 221, 226, 227, 240, 272, 302, 310, 313, 327, 342, 344, 370, 374, 388, 403, 406, 409, 413, 419, 425, 439, 449, 880, 948, 1015, 1055, 1132, 1165, 1385, 1443, 1680, 1755, 1785
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OFFSET
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1,2
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LINKS
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EXAMPLE
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sigma(1055) + phi(1055) = 1272 + 840 = 2112.
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MATHEMATICA
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Select[Range@ 1800, Reverse@ # == # &@ IntegerDigits[DivisorSigma[1, #] + EulerPhi@ #] &] (* Michael De Vlieger, Jul 22 2016 *)
Select[Range[2000], PalindromeQ[DivisorSigma[1, #]+EulerPhi[#]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 29 2020 *)
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PROG
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(PARI) ispal(n)=n=digits(n); Vecrev(n)==n
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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