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A224321
Primes without "7" as a digit that remain prime when any single digit is replaced with "7".
2
2, 3, 5, 11, 13, 19, 31, 41, 43, 61, 109, 139, 251, 643, 4933, 9433, 36493, 191416111, 1304119699
OFFSET
1,1
COMMENTS
No more terms < 10^13.
LINKS
G. L. Honaker, Jr. and Chris Caldwell, Prime Curios! 1304119699
Carlos Rivera, Puzzle 591
MATHEMATICA
lst = {}; n = 7; Do[If[PrimeQ[p], i = IntegerDigits[p]; If[FreeQ[i, n], t = 0; s = IntegerLength[p]; Do[If[PrimeQ@FromDigits@Insert[Drop[i, {d}], n, d], t++, Break[]], {d, s}]; If[t == s, AppendTo[lst, p]]]], {p, 36493}]; lst
Select[Prime[Range[4000]], DigitCount[#, 10, 7]==0&&AllTrue[FromDigits/@Table[ReplacePart[ IntegerDigits[#], n->7], {n, IntegerLength[#]}], PrimeQ]&] (* The program generates the first 17 terms of the sequence. *) (* Harvey P. Dale, Jun 09 2024 *)
CROSSREFS
Cf. A224319-A224320, A224322. Subsequence of A038615.
Sequence in context: A042999 A089194 A050229 * A053184 A228445 A287164
KEYWORD
base,more,nonn
AUTHOR
STATUS
approved