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 A056524 Palindromes with even number of digits. 15
 11, 22, 33, 44, 55, 66, 77, 88, 99, 1001, 1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 2002, 2112, 2222, 2332, 2442, 2552, 2662, 2772, 2882, 2992, 3003, 3113, 3223, 3333, 3443, 3553, 3663, 3773, 3883, 3993, 4004, 4114, 4224, 4334, 4444, 4554 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Concatenation of n with reverse of n (keeping leading zeros in the reverse). A178788(a(n)) = 0 for n > 1. - Reinhard Zumkeller, Jun 30 2010 All of the terms are divisible by eleven. - James Burling, Aug 08 2014 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..9999 FORMULA a(n) = n*10^A055642(n) + A004086(n). a(n) = 11 * A066492(n). MATHEMATICA d[n_]:=IntegerDigits[n]; Table[FromDigits[Join[x=d[n], Reverse[x]]], {n, 45}] (* Jayanta Basu, May 29 2013 *) Select[Flatten[Table[Range[10^n, 10^(n+1)-1], {n, 1, 3, 2}]], PalindromeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Feb 22 2018 *) PROG (Haskell) a056524 n = a056524_list !! (n-1) a056524_list = [read (ns ++ reverse ns) :: Integer | n <- [0..], let ns = show n] -- Reinhard Zumkeller, Dec 28 2011 (Python) def a(n): s = str(n); return int(s + s[::-1]) print([a(n) for n in range(1, 46)]) # Michael S. Branicky, Nov 02 2021 CROSSREFS Cf. A002113, A004086, A056525, A066492. Cf. A020338, A055642, A178788. Cf. A110745 (permutation). Sequence in context: A240927 A272655 A333440 * A110745 A280826 A020338 Adjacent sequences: A056521 A056522 A056523 * A056525 A056526 A056527 KEYWORD base,easy,nonn AUTHOR Henry Bottomley, Jun 16 2000 STATUS approved

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Last modified August 8 02:48 EDT 2024. Contains 375018 sequences. (Running on oeis4.)