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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
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
Sequence in context: A043990 A297829 A045068 * A206525 A216055 A034819
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.)