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).

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, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 2, 4, 0, 0, 0, 0, 0, 2

Offset: 1

Author

M. F. Hasler, Mar 15 2012

Keywords

• nonn
• base

Comments

Sequence A209063 is a subsequence which contains all (but not only) nonzero terms.

Crossrefs

Cf. A209063.

Programs

PARI

a(n)={my(r=A004086(n=prime(n))); sum(k=1, (2*n-1)\r, isprime(abs(n-k*r)))}

Formula

A209915 = A209914 o A000040.