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A028555
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Numbers n such that n*(n + 4) is a palindrome.
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0
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0, 1, 7, 14, 21, 33, 44, 144, 235, 269, 524, 1123, 1452, 1582, 5412, 8338, 8459, 11063, 11223, 23255, 73491, 145544, 262808, 266737, 281349, 1659022, 2705669, 3504083, 5040882, 7395091, 8308388, 14554452
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history;
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internal format)
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OFFSET
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1,3
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LINKS
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Table of n, a(n) for n=1..32.
Patrick De Geest, Palindromic Quasipronics of the form n(n+x)
Erich Friedman, What's Special About This Number? (See entries 1452, 1582, 5412, 8338, 8459.)
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MATHEMATICA
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Select[Range[0, 9999], PalindromeQ[#^2 + 4#] &] (* Alonso del Arte, Nov 10 2019 *)
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PROG
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(Scala) def palQ(n: Int, b: Int = 10): Boolean = n - Integer.parseInt(n.toString.reverse) == 0
(0 to 9999).filter((n: Int) => palQ(n * n + 4 * n)) // Alonso del Arte, Nov 10 2019
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CROSSREFS
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Cf. A028336.
Sequence in context: A189931 A164005 A100451 * A061823 A018890 A118502
Adjacent sequences: A028552 A028553 A028554 * A028556 A028557 A028558
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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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STATUS
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approved
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