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A125589 Smallest n-digit base-10 deletable prime. 1
2, 13, 103, 1013, 10039, 100103, 1000193, 10000931, 100001903, 1000003957, 10000003957, 100000013957, 1000000030957, 10000000301957, 100000000730957, 1000000000730957, 10000000003632979, 100000000007309357 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A prime p is a base-b deletable prime if when written in base b it has the property that removing some digit leaves either the empty string or another deletable prime. "Digit" means digit in base b.

Deleting a digit cannot leave any leading zeros in the new string. For example, deleting the 2 in 2003 to obtain 003 is not allowed.

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

b = 10; a = {2}; d = {2, 3, 5, 7};

For[n = 2, n <= 6, n++,

  found = False;

  p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &];

  For[i = 1, i <= Length[p], i++,

   c = IntegerDigits[p[[i]], b];

   For[j = 1, j <= n, j++,

    t = Delete[c, j];

    If[t[[1]] == 0, Continue[]];

    If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]];

     If[! found , AppendTo[a, p[[i]]]]; found = True; Break[]]];

]]; a (* Robert Price, Nov 13 2018 *)

CROSSREFS

Cf. A080608, A096243, A096246, A125590.

Sequence in context: A046893 A126036 A113598 * A007809 A259146 A103513

Adjacent sequences:  A125586 A125587 A125588 * A125590 A125591 A125592

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Jan 07 2007

EXTENSIONS

a(6) - a(8) from Michael Kleber, Jan 08 2007

a(9) - a(14) from Phil Carmody, Jan 09 2007

a(15) - a(18) from Joshua Zucker, Jan 09 2007

STATUS

approved

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Last modified December 15 22:02 EST 2019. Contains 330012 sequences. (Running on oeis4.)