A047813 - OEIS

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A047813

Largest palindromic substring of n.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 11, 2, 3, 4, 5, 6, 7, 8, 9, 2, 2, 22, 3, 4, 5, 6, 7, 8, 9, 3, 3, 3, 33, 4, 5, 6, 7, 8, 9, 4, 4, 4, 4, 44, 5, 6, 7, 8, 9, 5, 5, 5, 5, 5, 55, 6, 7, 8, 9, 6, 6, 6, 6, 6, 6, 66, 7, 8, 9, 7, 7, 7, 7, 7, 7, 7, 77, 8, 9, 8, 8, 8, 8, 8, 8, 8, 8, 88, 9, 9, 9, 9, 9, 9, 9

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

COMMENTS

a(n) = A262188(n,A262190(n)-1). - Reinhard Zumkeller, Sep 14 2015

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Index entries for sequences related to palindromes

EXAMPLE

a(1313) = Max{1,3,131,313} = 313.

MATHEMATICA

palQ[n_Integer, base_Integer] := Module[{idn = IntegerDigits[n, base]}, idn == Reverse[ idn]]; f[n_] := Block[{id = IntegerDigits@ n, mx = -Infinity}, k = Length@ id; While[k > 0 && mx == -Infinity, mx = Max[mx, Select[ FromDigits@# & /@ Partition[id, k, 1], palQ[#, 10] &]]; k--]; mx] (* Robert G. Wilson v, Aug 24 2011 *)

lps[n_]:=Module[{idn=IntegerDigits[n]}, Max[FromDigits/@Select[ Flatten[ Table[ Partition[ idn, i, 1], {i, Length[idn]}], 1], #==Reverse[#]&]]]; Array[ lps, 100, 0] (* Harvey P. Dale, Jan 09 2015 *)

PROG

(Haskell)

a047813 = last . a262188_row

-- Reinhard Zumkeller, Sep 14 2015, Aug 23 2011

(Python)

def c(s): return (s[0] != "0" or s == "0") and s == s[::-1]

def a(n):

s = str(n)

ss = (s[i:j] for i in range(len(s)) for j in range(i+1, len(s)+1))

return max(int(w) for w in ss if c(w))

print([a(n) for n in range(96)]) # Michael S. Branicky, Sep 18 2022

CROSSREFS