A029971 Palindromic primes in base 3.

2, 13, 23, 151, 173, 233, 757, 937, 1093, 1249, 1429, 1487, 1667, 1733, 1823, 1913, 1979, 2069, 8389, 9103, 10111, 12301, 14951, 16673, 16871, 18593, 60103, 60913, 61507, 63127, 69697, 73243, 78979, 80599, 82003, 82813, 83407, 85027

Offset

1,1

Comments

Intersection of A000040 and A014190. - Michel Marcus, Aug 19 2015

Links

Chai Wah Wu, Table of n, a(n) for n = 1..3004

P. De Geest, World!Of Palindromic Primes

Maple

N:= 14: # to get all terms < 3^N
Res:= 2:
digrev:=proc(n) local L;
  L:= convert(n, base, 3);
  add(L[-i]*3^(i-1), i=1..nops(L))
end proc;
for d from 2 to N do
  if d::even then
    m:= d/2;
    Res:= Res, op(select(isprime, [seq](n*3^m + digrev(n), n=3^(m-1)..3^m-1)));
  else
    m:= (d-1)/2;
    Res:= Res, op(select(isprime, [seq](seq(n*3^(m+1)+y*3^m+digrev(n),
      y=0..2), n=3^(m-1)..3^m-1)));
  fi
od:
Res; # Robert Israel, Aug 19 2015

Mathematica

Do[s = RealDigits[n, 3][[1]]; If[PrimeQ[n], If[FromDigits[s] == FromDigits[Reverse[s]], Print[n]]], {n, 1, 8500}]
Select[Prime[Range[8300]], Reverse[x = IntegerDigits[#, 3]] == x &] (* Jayanta Basu, Jun 23 2013 *)

Prog

(PARI) lista(nn) = forprime(p=2, nn, if ((d=digits(p, 3)) && (Vecrev(d)==d), print1(p, ", "))); \\ Michel Marcus, Aug 19 2015

Crossrefs

Cf. A117698 (in base 3), A014190.

Sequence in context: A093301 A079397 A118524 * A243619 A243620 A090526

Adjacent sequences: A029968 A029969 A029970 * A029972 A029973 A029974

Keyword

nonn,base

Author

Patrick De Geest

Status

approved