

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
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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

Table of n, a(n) for n=1..60.


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



