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A096238 Number of n-digit base-5 deletable primes. 0
2, 6, 14, 32, 69, 156, 377, 855, 2072, 5131, 12922, 32619, 83945, 217305, 571560, 1517012, 4056107 (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..17.

MATHEMATICA

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

For[n = 2, n <= 8, n++,

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

  ct = 0;

  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]]]; ct++;

     Break[]]]];

  AppendTo[a, ct]];

a (* Robert Price, Nov 12 2018 *)

CROSSREFS

Cf. A080608, A080603, A096235-A096246.

Sequence in context: A301554 A217941 A232434 * A074878 A065495 A131352

Adjacent sequences:  A096235 A096236 A096237 * A096239 A096240 A096241

KEYWORD

nonn,base,more

AUTHOR

Michael Kleber, Feb 28 2003

EXTENSIONS

12 more terms from Ryan Propper, Jul 19 2005

STATUS

approved

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Last modified December 11 03:29 EST 2018. Contains 318049 sequences. (Running on oeis4.)