A328932 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A328932

Number of primes that are a concatenation of two positive integers whose sum is prime(n).

1, 0, 2, 2, 4, 3, 2, 6, 5, 9, 6, 7, 10, 11, 12, 14, 12, 16, 14, 17, 12, 15, 16, 20, 19, 19, 20, 17, 23, 23, 18, 27, 28, 24, 30, 25, 26, 26, 28, 30, 27, 30, 32, 27, 25, 27, 37, 42, 38, 32, 32, 33, 30, 39, 38, 36, 43, 38, 43, 42, 36, 36, 47, 47, 49, 38, 45, 48, 51, 50

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A328903(A000040(n)).

EXAMPLE

a(3) = 2 because primes 23, 41 are concatenations of prime(3) = 5 = 2 + 3 = 4 + 1.

MAPLE

a:= n-> (p-> add(`if`(isprime(parse(cat(i,

p-i))), 1, 0), i=1..p-1))(ithprime(n)):