A224321 Primes without "7" as a digit that remain prime when any single digit is replaced with "7".

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

Table of n, a(n) for n=1..19.

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

Adjacent sequences: A224318 A224319 A224320 * A224322 A224323 A224324

Keyword

base,more,nonn

Author

Arkadiusz Wesolowski, Apr 03 2013

Status

approved