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A180613 The number of palindromic primes in the first n terms of A006530. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A121759 A265310 A263283 * 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

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Last modified December 6 06:58 EST 2016. Contains 278775 sequences.