This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A154270 Primes of the form XYX, where Y is a single digit. 7
 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 11311, 11411, 13313, 13513, 13613, 13913, 17117, 17317, 17417, 19219, 19319, 19819, 19919, 21121, 21221, 21521, 21821, 23623, 27127, 27427, 27527, 27827, 29129 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Join[{101}, f[n_]:=Block[{len=Floor[Log[10, n]+1]}, Select[10^(1+len) n+10^len*Table[k (10^1-1)/9, {k, 9}]+n, PrimeQ@#&]]; Array[f, 40]//Flatten]; Vincenzo Librandi, Jul 27 2012 Select[Flatten[Table[FromDigits[Flatten[Join[{IntegerDigits[n], i, IntegerDigits[ n]}]]], {n, 50}, {i, 0, 9}]], PrimeQ] (* Harvey P. Dale, Aug 22 2014 *) PROG (MAGMA) [p: d in [0..9], n in [1..40 by 2] | IsPrime(p) where p is n*10^(t+1)+d*10^t+n where t is #Intseq(n)]; // Vincenzo Librandi, Sep 14 2013 CROSSREFS Cf. A162423, A214290, A214291. Sequence in context: A075793 A319049 A052086 * A056730 A077798 A089360 Adjacent sequences:  A154267 A154268 A154269 * A154271 A154272 A154273 KEYWORD nonn,base AUTHOR Vincenzo Librandi, Jan 06 2009 EXTENSIONS Inserted 19919. R. J. Mathar, Jan 07 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 16 22:43 EST 2018. Contains 317275 sequences. (Running on oeis4.)