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.
Select[Range[300],PrimeQ[FromDigits[Join[{9},IntegerDigits[#],{9}]]]&] (* Harvey P. Dale, Jul 20 2012 *)
from sympy import isprime
def ok(n): return isprime(int('9' + str(n) + '9'))
print([k for k in range(250) if ok(k)]) # Michael S. Branicky, Sep 04 2022
2437 prefixed and followed with a pair of digits from (1,2,3,4,5,6,7,8,9) never yields a prime, e.g., '9'2437'1' = 7 * 37 * 43 * 83.
isA032734 := proc(n) for k from 1 to 9 do for k2 from 1 to 9 do dgs := [k,op(convert(n,base,10)),k2] ; dgsn := add( op(i,dgs)*10^(i-1),i=1..nops(dgs)) ; if isprime(dgsn) then return false; end if; end do: end do: return true; end proc: for n from 1 to 50000 do if isA032734(n) then printf("%d,",n); end if; end do: # R. J. Mathar, Oct 22 2011 filter:= proc(n) local d,i,j; d:= 10^(ilog10(n)+2); not ormap(isprime,[seq(seq(d*i+10*n+j,j=[1,3,5,7,9]),i=1..9)]) end proc: select(filter,[$1..10^5]); # Robert Israel, Jul 07 2016
ok[n_] := With[{id = IntegerDigits[n]}, Select[ Flatten[ Table[ FromDigits[ Join[{j}, id, {k}]], {j, 1, 9}, {k, 1, 9}], 1], PrimeQ, 1] == {}]; A032734 = {}; n = 1; While[n < 50000, If[ok[n], Print[n]; AppendTo[A032734, n]]; n++]; A032734(* Jean-François Alcover, Nov 23 2011 *)
Select[Range[50000],NoneTrue[Flatten[Table[FromDigits[Join[{x}, IntegerDigits[ #],{y}]],{x,9},{y,9}]],PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 07 2018 *)
is_A032734(n)=p=10^#Str(n*=10);forstep(k=n+p,n+9*p,p,nextprime(k)>k+9 || return);1 \\ M. F. Hasler, Oct 22 2011
from sympy import isprime
def ok(n):
s, fdigs, edigs = str(n), "123456789", "1379"
return not any(isprime(int(f+s+e)) for f in fdigs for e in edigs)
print([k for k in range(10**5) if ok(k)]) # Michael S. Branicky, Sep 05 2022
Select[Range[250],PrimeQ[FromDigits[Join[{3},IntegerDigits[#],{3}]]]&] (* Harvey P. Dale, Apr 18 2012 *)
from sympy import isprime
def ok(n): return isprime(int('3' + str(n) + '3'))
print([k for k in range(220) if ok(k)]) # Michael S. Branicky, Sep 04 2022