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A096236 Number of n-digit base-3 deletable primes. 2
1, 2, 4, 7, 13, 24, 38, 72, 122, 226, 400, 684, 1246, 2381, 4384, 8330, 15839, 30617, 58764, 113987, 221994, 434498, 852036, 1673320, 3296641, 6509179 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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..26.

MATHEMATICA

b = 3; a = {1}; d = {2};

For[n = 2, n <= 10, 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: A018182 A005595 A296689 * A002574 A069765 A090427

Adjacent sequences:  A096233 A096234 A096235 * A096237 A096238 A096239

KEYWORD

nonn,more,base

AUTHOR

Michael Kleber, Feb 28 2003

EXTENSIONS

More terms from John W. Layman, Dec 14 2004

11 more terms from Ryan Propper, Jul 19 2005

STATUS

approved

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Last modified December 10 23:33 EST 2018. Contains 318049 sequences. (Running on oeis4.)