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 A050701 If composite k and its reverse are different and have same number of prime factors, then the larger of them is a term of the sequence. 2
 51, 62, 85, 93, 94, 221, 302, 321, 341, 381, 413, 442, 492, 493, 502, 511, 513, 514, 522, 524, 533, 534, 551, 553, 561, 562, 574, 581, 582, 604, 605, 621, 622, 623, 642, 663, 682, 685, 705, 711, 723, 734, 741, 766, 771, 781, 794, 805, 814, 817 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..50. EXAMPLE a(n)=341 -> reverse(a(n)) = 143 gives the pair (143,341) of which only the larger value 341 is retained. MATHEMATICA rev[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[825], !PrimeQ[#]&&PrimeOmega[#]==PrimeOmega[x=rev[#]]&&#>x&] (* Jayanta Basu, May 31 2013 *) PROG (PARI) isok(m) = my(k=fromdigits(Vecrev(digits(m)))); (m%10) && !isprime(m) && (m>k) && (bigomega(k) == bigomega(m)); \\ Michel Marcus, Aug 18 2021 CROSSREFS Cf. A004086, A050699, A050700. Sequence in context: A043990 A297829 A045068 * A206525 A216055 A034819 Adjacent sequences: A050698 A050699 A050700 * A050702 A050703 A050704 KEYWORD nonn,base AUTHOR Patrick De Geest, Aug 15 1999 EXTENSIONS Revised by Editors of OEIS, Oct 19 2019 Incorrect 394 and 523 removed and name clarified by Sean A. Irvine, Aug 17 2021 STATUS approved

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Last modified July 19 14:36 EDT 2024. Contains 374407 sequences. (Running on oeis4.)