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A110751
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Numbers n such that n and its digital reversal have the same prime divisors.
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14
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1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494
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OFFSET
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1,2
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COMMENTS
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Contains the palindromes A002113 as a subsequence. 1089 and 2178 are the first two non-palindromic terms. Any number of concatenations of 1089 with itself or 2178 with itself gives a term; e.g. 10891089 etc. Hence there are infinitely many non-palindromic terms. They are given in A110819.
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LINKS
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EXAMPLE
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1089 = 3^2*11^2, 9801 = 3^4*11^2.
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MATHEMATICA
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Select[ Range[ 500], First /@ FactorInteger[ # ] == First /@ FactorInteger[ FromDigits[ Reverse[ IntegerDigits[ # ]]]] &] (* Robert G. Wilson v *)
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PROG
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(PARI) is_A110751(n)={ local(r=eval(concat(vecextract(Vec(Str(n)), "-1..1")))); r==n || factor(r)[, 1]==factor(n)[, 1] } /* M. F. Hasler */
(Python)
from sympy import primefactors
A110751 = [n for n in range(1, 10**5) if primefactors(n) == primefactors(int(str(n)[::-1]))] # Chai Wah Wu, Aug 14 2014
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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Corrected comment, added PARI code. - M. F. Hasler, Nov 16 2008
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STATUS
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approved
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