cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A208361 "1-ply" palindromic primes; see Comments.

Original entry on oeis.org

2, 3, 5, 7, 100030001, 100050001, 100060001, 100111001, 100131001, 100161001, 100404001, 100656001, 100707001, 100767001, 100888001, 100999001, 101030101, 101060101, 101141101, 101171101, 101282101, 101292101, 101343101, 101373101, 101414101, 101424101, 101474101
Offset: 1

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Author

Alvin Hoover Belt, Feb 25 2012

Keywords

Comments

From the Ribenboim book: palindromic primes whose length is not a palindromic prime.
a(42046) = 999727999 and a(42047) = 1000008000001. [Charles R Greathouse IV, Feb 26 2012]

Examples

			2 is a palindromic prime of 1 digit, but 1 is not prime, therefore 2 is a 1-ply palindromic prime.
100050001 is a palindromic prime of 9 digits, but 9 is composite, therefore 100050001 is a 1-ply palindromic prime.
		

References

  • Paulo Ribenboim, The New Book of Prime Number Records, Springer-Verlag New York Inc., 1996, p. 160-161.

Crossrefs

Cf. A109830.

Programs

  • Mathematica
    t = {2, 3, 5, 7}; n = 10000; While[n <= 99999 && Length[t] < 100, n = n + 1; d = IntegerDigits[n]; d2 = FromDigits[Join[d, Rest[Reverse[d]]]]; If[PrimeQ[d2], AppendTo[t, d2]]]; t (* T. D. Noe, Jun 03 2013 *)

Extensions

a(5)-a(26) from Charles R Greathouse IV, Feb 26 2012