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A322172
Primes that are not base-7 deletable primes (written in base 10).
1
7, 11, 13, 29, 43, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 107, 109, 113, 127, 151, 157, 173, 179, 181, 193, 197, 211, 229, 239, 257, 269, 271, 277, 281, 283, 307, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499
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.
Complement of all primes and A321910.
LINKS
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[]]]]; Complement[Table[Prime[n], {n, PrimePi[Last[d]]}], d] (* Robert Price, Dec 06 2018 *)
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Robert Price, Nov 29 2018
STATUS
approved