This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
a(2)=227 is a term because all digits are equal to 2 except one.
a(2)=883 is a term because all digits are equal to 8 except one.
a(2)=6661 is a term because all digits are equal to 6 except one.
Select[FromDigits/@Flatten[Table[PadLeft[{pd},n,6],{pd,{1,7}},{n,3,30}],1],PrimeQ]//Sort (* Harvey P. Dale, Sep 01 2021 *)
3331 is a term because all digits are equal to 3 except the last one.
77773 is a term because all digits are equal to 7 except the last one.
99991 is a term because all digits are equal to 9 except the last one.
R:= NULL: count:= 0:
for n from 3 to 999 do
for d in [9,3] do
if isprime(10^n - d) then
R:= R, 10^n-d; count:= count+1;
fi
od od:
R;
Join[{11},Select[Flatten[Table[FromDigits[Join[PadRight[{},n,1],{d},PadRight[{},n,1]]],{n,26},{d,Cases[Range[0,9],Except[1]]}]],PrimeQ]] (* Harvey P. Dale, Nov 04 2024 *)
print1(11); for(L=1,19,for(d=0,9,d!=1 && ispseudoprime(p=10^(2*L+1)\9+(d-1)*10^L) && print1(","p))) \\ M. F. Hasler, Feb 07 2020
lst = {}; Do[If[PrimeQ[n] && SortBy[Tally[IntegerDigits[n]], Last][[-1, -1]] == IntegerLength[n] - 1, AppendTo[lst, n]], {n, 101, 10^3}]; lst (* Arkadiusz Wesolowski, Sep 18 2011 *)
lst = {}; Do[r = (10^n - 1)/9; Do[AppendTo[lst, DeleteCases[Select[FromDigits[Permutations[Append[IntegerDigits[a*r], d]]], PrimeQ], r | 2 | 3 | 5 | 7]], {a, 9}, {d, 0, 9}], {n, 2, 6}]; Sort[Flatten[lst]] (* Arkadiusz Wesolowski, Sep 22 2011 *)
from sympy import isprime
from itertools import count, islice
def agen(): # generator of terms
for d in count(3):
ds = set()
for end in "1379":
ds.update(int(c*(d-1) + end) for c in "123456789" if c != end)
for diff in "0123456789":
if end == diff: continue
cands = (end*i + diff + end*(d-1-i) for i in range(d-1))
ds.update(int(t) for t in cands if t[0] != "0")
yield from sorted(t for t in ds if isprime(t))
print(list(islice(agen(), 52))) # Michael S. Branicky, May 17 2022
127 is not in the sequence since 271 is prime but neither 217 nor 721 are; to be in the sequence all of these numbers would have to be prime, and they would form an orbit of size 4 (by Name, permutations of these numbers ending in 2 are not considered). 241 and 421 are in the sequence and form an orbit of size 2 since these primes can be obtained by permutations that forbid the units digit to be an even number. 569 and 659 are in the sequence since these primes can be obtained by permutations that forbid the units digit to be either 5 or an even number.
filter:= proc(n) local L,m,i,t;
if not isprime(n) then return false fi;
L:= convert(n,base,10);
m:=nops(L);
for i in select(t -> member(L[t],[1,3,7,9]), [$1..m]) do
for t in combinat:-permute(subsop(i=NULL, L)) do
if not isprime(L[i]+add(10^j*t[j],j=1..m-1)) then
return false fi
od od;
true
end proc:
select(filter, [2,seq(i,i=3..2000,2)]); # Robert Israel, Aug 31 2018
Select[Prime@Range[120], AllTrue[FromDigits /@ Permutations[IntegerDigits@ #], PrimeQ[#] || MemberQ[{0, 2, 4, 5, 6, 8}, Mod[#, 10]] &] &] (* Giovanni Resta, Jul 14 2018 *)
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