login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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: A062759 A121758 A121759 * A072778 A178787 A034326

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 18 08:30 EST 2014. Contains 252114 sequences.