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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

Derek Orr, Table of n, a(n) for n = 1..1000

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

Cf. A002113, A110819.

Sequence in context: A342826 A266140 A297271 * A147882 A002113 A227858

Adjacent sequences:  A110748 A110749 A110750 * A110752 A110753 A110754

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 August 4 05:02 EDT 2021. Contains 346442 sequences. (Running on oeis4.)