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A321910 Base-7 deletable primes (written in base 10). 2
2, 3, 5, 17, 19, 23, 31, 37, 41, 47, 101, 103, 131, 137, 139, 149, 163, 167, 191, 199, 223, 227, 233, 241, 251, 263, 293, 311, 313, 317, 331, 691, 709, 719, 727, 733, 787, 823, 853, 877, 887, 919, 929, 937, 977, 983, 997, 1013, 1019, 1021, 1031, 1049, 1129, 1171, 1367, 1399, 1409, 1511 (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.

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

Robert Price, Table of n, a(n) for n = 1..808

MATHEMATICA

b = 7; d = {};

p = Select[Range[2, 10000], PrimeQ[#] &];

For[i = 1, i <= Length[p], i++,

  c = IntegerDigits[p[[i]], b];

  If[Length[c] == 1, AppendTo[d, p[[i]]]; Continue[]];

  For[j = 1, j <= Length[c], j++,

   t = Delete[c, j];

   If[t[[1]] == 0, Continue[]];

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

d (* Robert Price, Dec 06 2018 *)

CROSSREFS

Cf. A080608, A080603, A096235-A096246.

Sequence in context: A214697 A035089 A045313 * A045314 A129943 A129673

Adjacent sequences:  A321907 A321908 A321909 * A321911 A321912 A321913

KEYWORD

nonn,base,easy

AUTHOR

Robert Price, Nov 29 2018

STATUS

approved

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Last modified March 21 12:12 EDT 2019. Contains 321369 sequences. (Running on oeis4.)