A171691 Number of unordered partitions {k1, k2} of n such that k1 and k2 are nonnegative nonprimes A141468.

1, 1, 0, 1, 1, 1, 1, 2, 2, 3, 1, 3, 2, 3, 3, 5, 2, 5, 3, 5, 4, 6, 3, 7, 5, 7, 5, 8, 5, 9, 6, 8, 7, 10, 7, 12, 7, 9, 9, 12, 8, 13, 9, 12, 10, 13, 9, 15, 11, 15, 11, 15, 11, 17, 13, 16, 13, 17, 13, 20, 14, 16, 15, 20, 15, 22, 15, 18, 17, 22, 16, 23, 17, 21, 18, 23, 18, 26, 18, 23

Offset

1,8

Links

Andrew Howroyd, Table of n, a(n) for n = 1..10000

Example

a(1) = 1 because 1 = 0 + 1.
a(2) = 1 because 2 = 1 + 1.
a(3) = 0.
a(4) = 1 because 4 = 0 + 4.
a(5) = 1 because 5 = 1 + 4.
a(6) = 1 because 6 = 0 + 6.
a(7) = 1 because 7 = 1 + 6.
a(8) = 2 because 8 = 0 + 8 = 4 + 4.

Prog

(PARI) a(n)={sum(i=0, n\2, (i<2 || !isprime(i)) && !isprime(n-i))} \\ Andrew Howroyd, Jan 05 2020

Crossrefs

Cf. A062610, A141468, A224708.

Sequence in context: A160650 A304092 A339669 * A088904 A241568 A335017

Adjacent sequences: A171688 A171689 A171690 * A171692 A171693 A171694

Keyword

nonn

Author

Juri-Stepan Gerasimov, Dec 15 2009

Extensions

Name clarified and terms a(55) and beyond from Andrew Howroyd, Jan 05 2020

Status

approved