A180613 The number of palindromic primes in the first n terms of A006530.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13, 14, 14, 15, 15, 16, 17, 18, 18, 19, 20, 20, 21, 22, 22, 23, 23, 24, 25, 25, 26, 27, 27, 27, 27, 28, 28, 29, 29, 30, 31, 31, 31, 32, 33, 34, 34, 34, 34, 35, 36, 37, 37, 37, 37, 38, 38, 38, 39, 40, 40, 41, 41, 41, 41, 42, 42, 43, 43, 43, 44

Offset

1,3

Links

Table of n, a(n) for n=1..75.

Formula

#{A006530(i): i<=n and A006530(i) in A002385}.

Example

Of the first n=13 terms of A006530, all but two (1 and 13 being the exceptions) are also in A002385, which leads to a(13)=11.

Maple

A006530 := proc(n) if n = 1 then 1; else numtheory[factorset](n) ; max(op(%)) ; end if; end proc:
isA002113 := proc(n) dgs := convert(n, base, 10) ; for i from 1 to nops(dgs) do if op(i, dgs) <> op(-i, dgs) then return false; end if; end do: return true; end proc:
isA002385 := proc(n) isprime(n) and isA002113(n) ; end proc:
A180613 := proc(n) a := 0 ; for i from 1 to n do if isA002385(A006530(i)) then a := a+1 ; end if; end do: a; end proc:
seq(A180613(n), n=1..40) ; # R. J. Mathar, Sep 25 2010

Crossrefs

Sequence in context: A265310 A291576 A355221 * A254948 A072778 A178787

Adjacent sequences: A180610 A180611 A180612 * A180614 A180615 A180616

Keyword

base,nonn,less

Author

Giovanni Teofilatto, Sep 12 2010

Extensions

Definition clarified by R. J. Mathar, Sep 25 2010

Status

approved