

A224713


The number of unordered partitions {a, b} of the even numbers 2n such that a or b is composite and the other is prime.


1



0, 0, 1, 1, 1, 2, 2, 2, 2, 3, 3, 2, 4, 5, 3, 6, 4, 3, 8, 6, 4, 7, 7, 4, 7, 9, 5, 10, 9, 4, 12, 8, 6, 14, 9, 7, 11, 11, 7, 13, 13, 6, 14, 15, 5, 16, 15, 10, 18, 13, 9, 16, 16, 11, 16, 15, 9, 18, 19, 6, 23, 20, 10, 24, 17, 13, 21, 22, 16, 19, 19, 12, 23, 24
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OFFSET

1,6


LINKS

J. Stauduhar, Table of n, a(n) for n = 1..10000


EXAMPLE

For n = 3, 2n=6. In the set {{5, 1}, {4, 2}, {3, 3}}, {4, 2} is the only partition that satisfies the requirements, so a(3) = 1.
For n = 10, 2n=20 and we have partitions {18, 2}, {15, 5}, and {11, 9}, so a(10) = 3.


PROG

(PARI) a(n)=my(s); n*=2; forprime(p=2, n4, s+=!isprime(np)); s \\ Charles R Greathouse IV, Apr 30 2013


CROSSREFS

Subsequence of A224712.
Sequence in context: A143901 A115263 A055894 * A168557 A194320 A231555
Adjacent sequences: A224710 A224711 A224712 * A224714 A224715 A224716


KEYWORD

nonn,easy


AUTHOR

J. Stauduhar, Apr 20 2013


STATUS

approved



