login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A096241 Number of n-digit base-8 deletable primes. 0
4, 14, 50, 238, 1123, 5792, 30598, 166056, 927639, 5308458, 30984757 (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..11.

MATHEMATICA

b = 8; a = {4}; d = {2, 3, 5, 7};

For[n = 2, n <= 5, 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 13 2018 *)

CROSSREFS

Cf. A080608, A080603, A096235-A096246.

Sequence in context: A062807 A117421 A034743 * A283108 A211303 A247415

Adjacent sequences:  A096238 A096239 A096240 * A096242 A096243 A096244

KEYWORD

nonn,base,more

AUTHOR

Michael Kleber, Feb 28 2003

EXTENSIONS

5 more terms from Ryan Propper, Jul 19 2005

a(11) from D. S. McNeil, Dec 08 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 11 18:19 EST 2019. Contains 329925 sequences. (Running on oeis4.)