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A248889
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Palindromic in base 10 and 18.
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2
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 171, 323, 343, 505, 595, 686, 848, 1661, 2112, 3773, 23332, 46664, 69996, 262262, 583385, 782287, 859958, 981189, 1254521, 1403041, 1832381, 39388393, 54411445, 55499455, 88844888, 118919811, 191010191
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OFFSET
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1,3
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COMMENTS
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a(54) > 10^12.
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LINKS
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EXAMPLE
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848 in decimal is 2B2 in base 18, so 848 is in the sequence.
1661 in decimal is 525 in base 18, so 1661 is in the sequence.
1771 in decimal is 587 in base 18, which is not a palindrome, so 1771 is not in the sequence.
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MAPLE
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IsPalindromic := proc(n, Base)
local Conv, i;
Conv := convert(n, base, Base);
for i from 1 to nops(Conv) / 2 do
if Conv [i] <> Conv [nops(Conv) + 1 - i] then
return false;
fi:
od:
true;
end proc:
Base := 18;
A := [];
for i from 1 to 10^6 do:
S := convert(i, base, 10);
V := 0;
if i mod 10 = 0 then
next;
fi;
for j from 1 to nops(S) do:
V := V * 10 + S [j];
od:
for j from 0 to 10 do:
V1 := V * 10^(nops(S) + j) + i;
if IsPalindromic(V1, Base) then
A := [op(A), V1];
fi;
od:
V1 := (V - (V mod 10)) * 10^(nops(S) - 1) + i;
if IsPalindromic(V1, Base) then
A := [op(A), V1];
fi;
od:
sort(A);
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MATHEMATICA
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palindromicQ[n_, b_:10] := TrueQ[IntegerDigits[n, b] == Reverse[IntegerDigits[n, b]]]; Select[Range[0, 499], palindromicQ[#] && palindromicQ[#, 18] &] (* Alonso del Arte, Mar 21 2015 *)
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PROG
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(PARI) isok(n) = (n==0) || ((d = digits(n, 10)) && (Vecrev(d) == d) && (d = digits(n, 18)) && (Vecrev(d) == d)); \\ Michel Marcus, Mar 14 2015
(Magma) [n: n in [0..2*10^7] | Intseq(n) eq Reverse(Intseq(n)) and Intseq(n, 18) eq Reverse(Intseq(n, 18))]; // Vincenzo Librandi, Mar 21 2015
(Python)
def palgen10(l): # generator of palindromes of length <= 2*l
....if l > 0:
........yield 0
........for x in range(1, l+1):
............n = 10**(x-1)
............n2 = n*10
............for y in range(n, n2):
................s = str(y)
................yield int(s+s[-2::-1])
............for y in range(n, n2):
................s = str(y)
................yield int(s+s[::-1])
def palcheck(n, b): # check if n is a palindrome in base b
....s = digits(n, b)
....return s == s[::-1]
A248889_list = [n for n in palgen10(9) if palcheck(n, 18)]
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CROSSREFS
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Cf. A007632, A007633, A029961, A029962, A029963, A029964, A029965, A029966, A029967, A029968, A029969, A029970, A028731, A097855, A248899
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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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