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A110751 Numbers n such that n and its digital reversal have the same prime divisors. 14
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
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.
LINKS
EXAMPLE
1089 = 3^2*11^2, 9801 = 3^4*11^2.
MATHEMATICA
Select[ Range[ 500], First /@ FactorInteger[ # ] == First /@ FactorInteger[ FromDigits[ Reverse[ IntegerDigits[ # ]]]] &] (* Robert G. Wilson v *)
PROG
(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
CROSSREFS
Sequence in context: A342826 A266140 A297271 * A147882 A002113 A227858
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Aug 11 2005
EXTENSIONS
Edited and extended by Robert G. Wilson v, Sep 21 2005
Corrected comment, added PARI code. - M. F. Hasler, Nov 16 2008
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)