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A029971 Palindromic primes in base 3. 12
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Intersection of A000040 and A014190. - Michel Marcus, Aug 19 2015
LINKS
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
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified February 28 14:20 EST 2024. Contains 370400 sequences. (Running on oeis4.)