A057877 a(n) = smallest n-digit prime in A057876.

23, 113, 1531, 12239, 111317, 1111219, 11119291, 111111197, 1111113173, 11111133017, 111111189919, 1111111411337, 11111111161177, 111111111263311, 1111111111149119, 11111111111179913, 111111111111118771, 1111111111111751371, 11111111111111111131, 111111111111113129773, 1111111111111111337111

Offset

2,1

Links

Table of n, a(n) for n=2..22.

Example

1531 gives primes 53, 131 and 151 after dropping digits 1, 5 and 3.

Maple

filter:= proc(n) local L, d, Lp;
  if not isprime(n) then return false fi;
  L:= convert(n, base, 10);
  for d in convert(L, set) do
    Lp:= subs(d=NULL, L);
    if Lp=[] or Lp[-1] = 0 then return false fi;
    if not isprime(add(Lp[i]*10^(i-1), i=1..nops(Lp))) then return false fi;
  od;
  true
end proc:
Res:= NULL:
for t from 1 to 21 do
  for x from (10^(t+1)-1)/9 by 2 do
    if filter(x) then Res:= Res, x; break fi
  od
od:
Res; # Robert Israel, Jul 13 2018

Mathematica

Do[k = (10^n - 1)/9; While[d = IntegerDigits[k]; !PrimeQ[k] || !PrimeQ[ FromDigits[ DeleteCases[d, 0]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 1]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 2]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 3]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 4]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 5]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 6]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 7]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 8]]] || !PrimeQ[ FromDigits[ DeleteCases[d, 9]]], k++ ]; Print[k], {n, 2, 19}]

Crossrefs

Cf. A057876, A057877, A057878, A057879, A057880, A057881, A057882, A057883, A051362, A034302, A034303, A034304, A034305.

Sequence in context: A288751 A070024 A111943 * A302530 A156568 A042026

Adjacent sequences: A057874 A057875 A057876 * A057878 A057879 A057880

Keyword

base,nonn

Author

Patrick De Geest, Oct 15 2000

Extensions

Extended by Robert G. Wilson v, Dec 17 2002

More terms from Robert Israel, Jul 13 2018

Status

approved