OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..500 (* First 140 terms from Paolo P. Lava *)
EXAMPLE
290183 is prime and also 2901853, 2901583, 2905183, 2950183 and 2590183.
MAPLE
with(numtheory);
A217064:=proc(q, x)
local a, b, c, i, n, ok;
for n from 5 to q do
a:=ithprime(n); b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od; a:=ithprime(n); ok:=1;
for i from 1 to b-1 do
c:=a+9*10^i*trunc(a/10^i)+10^i*x; if not isprime(c) then ok:=0; break; fi; od;
if ok=1 then print(ithprime(n)); fi; od; end:
A217064(1000000, 5);
MATHEMATICA
Select[Prime[Range[5, 1000]], AllTrue[FromDigits/@Table[ Insert[ IntegerDigits[ #], 5, n], {n, 2, IntegerLength[#]}], PrimeQ]&] (* Harvey P. Dale, Feb 20 2022 *)
PROG
(PARI) is(n)=my(v=concat([""], digits(n))); for(i=2, #v-1, v[1]=Str(v[1], v[i]); v[i]=5; if(i>2, v[i-1]=""); if(!isprime(eval(concat(v))), return(0))); isprime(n) \\ Charles R Greathouse IV, Sep 26 2012
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Paolo P. Lava, Sep 26 2012
STATUS
approved