cp's OEIS Frontend

A209915 Number of ways the n-th prime p(n) can be written as a multiple of its reversal A004086(p) +/- a prime q < p(n).

%I A209915 #9 Mar 30 2012 17:23:05
%S A209915 0,0,0,0,0,0,0,0,0,0,1,0,2,0,0,1,0,4,0,3,0,0,2,0,1,0,0,0,0,0,0,0,0,0,
%T A209915 0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,1,0,0,0,1,0,1,0,0,0,0,0,0,0,0,
%U A209915 0,0,0,0,0,0,0,0,0,0,3,0,0,2,4,0,0,0,0,0,2
%N A209915 Number of ways the n-th prime p(n) can be written as a multiple of its reversal A004086(p) +/- a prime q < p(n).
%C A209915 Sequence A209063 is a subsequence which contains all (but not only) nonzero terms.
%F A209915 A209915 = A209914 o A000040.
%o A209915 (PARI) a(n)={my(r=A004086(n=prime(n))); sum(k=1, (2*n-1)\r, isprime(abs(n-k*r)))}
%Y A209915 Cf. A209063.
%K A209915 nonn,base
%O A209915 1,13
%A A209915 _M. F. Hasler_, Mar 15 2012