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

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)):
seq(a(n), n=1..80);  # Alois P. Heinz, Oct 31 2019

Crossrefs

Subsequence of A328903.

Cf. A000040, A066686, A067754.

Sequence in context: A112154 A112155 A355476 * A341148 A209749 A248345

Adjacent sequences: A328929 A328930 A328931 * A328933 A328934 A328935

Keyword

nonn,base,easy

Author

Juri-Stepan Gerasimov, Oct 31 2019

Status

approved