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 A179826 Primes that can be obtained from composite numbers by interchanging the first and last digits. 2
 41, 61, 2, 3, 23, 43, 53, 83, 5, 7, 47, 67, 19, 29, 59, 89, 401, 601, 11, 211, 811, 911, 421, 521, 821, 31, 331, 431, 631, 41, 241, 541, 641, 251, 61, 461, 661, 71, 271, 571, 281, 881, 491, 691, 2, 3, 103, 503, 13, 613, 23, 223, 523, 823, 233, 433, 43, 443, 643, 53 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The composite number must contain at least two digits. Primes may be repeated; the reverted A002808(j) are investigated along increasing j and their trailing zeros become leading zeros and are dropped. [From R. J. Mathar, Jul 30 2010] LINKS EXAMPLE 41 is a prime from the composite number 14 by interchanging the first and last digit. 47 is a prime from the composite number 74 by interchanging the first and last digit. MATHEMATICA nonpr=Complement[Range[10, 1000], Prime[Range[PrimePi[1000]]]]; swtch[n_]:=Module[{idn=IntegerDigits[n], f, l, m}, f=First[idn]; l=Last[idn]; m=Most[Rest[idn]]; FromDigits[Join[{l}, m, {f}]]] Select[swtch[#]&/@nonpr, PrimeQ] [from Harvey P. Dale, Dec. 14, 2010] CROSSREFS Sequence in context: A222577 A116322 A153681 * A067832 A126242 A178057 Adjacent sequences:  A179823 A179824 A179825 * A179827 A179828 A179829 KEYWORD base,nonn AUTHOR Parthasarathy Nambi, Jul 29 2010 EXTENSIONS Minor edits by N. J. A. Sloane, Jul 29 2010 More terms from R. J. Mathar, Jul 30 2010 STATUS approved

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Last modified April 10 11:15 EDT 2021. Contains 342845 sequences. (Running on oeis4.)