A262558 Number of palindromic primes <= n.

0, 0, 1, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6

Offset

0,4

Comments

More than the usual number of terms are displayed in order to show the first 6.

Links

N. J. A. Sloane, Table of n, a(n) for n = 0..30103

Example

The sixth palindromic prime is 101, so a(101)=6.

Maple

# SEQPI: produces the pi function for a monotonic sequence a[]
# Returns list b[], where b[n+1} gives number of terms in range 0 to n.
# Generates at least M terms of b (if possible) and then stops at the next convenient stopping point.
SEQPI:=proc(a, M)  local b, la, L, i, s, at, ct, h:
if whattype(a) <> list then RETURN([]); fi:
la:=nops(a); b:=[]: L:=min(a[la], M);
ct:=0;
   s:=0;
for at from 1 to la do
   for i from s to a[at]-1 do b:=[op(b), ct]; od:
   ct:=ct+1;
   s:=a[at];
   if s>L then break; fi;
                    od:
b:=[op(b), ct];
RETURN(b);
end;
# Assume b2385 has the first 1000 terms of A002385
SEQPI(b2385, 20000):

Mathematica

Accumulate[Table[If[PrimeQ[n]&&PalindromeQ[n], 1, 0], {n, 0, 200}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 29 2017 *)

Crossrefs

Cf. A002113 (palindromes), A002385 (palindromic primes).

Sequence in context: A341167 A094235 A328003 * A156876 A137397 A239684

Adjacent sequences: A262555 A262556 A262557 * A262559 A262560 A262561

Keyword

nonn,base

Author

N. J. A. Sloane, Oct 15 2015

Status

approved