A347788 Number of compositions (ordered partitions) of n into at most 2 nonprime parts.

1, 1, 1, 0, 1, 2, 1, 2, 2, 3, 5, 2, 4, 4, 5, 5, 8, 4, 8, 6, 8, 7, 11, 6, 12, 9, 13, 9, 14, 10, 16, 12, 14, 13, 19, 13, 22, 14, 17, 17, 22, 16, 24, 18, 22, 19, 25, 18, 28, 21, 28, 21, 28, 22, 32, 25, 30, 25, 33, 26, 38, 28, 31, 29, 38, 29, 42, 30, 34, 33, 42

Offset

0,6

Links

Antti Karttunen, Table of n, a(n) for n = 0..10000

Mathematica

Table[Length@Flatten[Permutations/@IntegerPartitions[n, 2, Select[Range@n, !PrimeQ@#&]], 1], {n, 0, 70}] (* Giorgos Kalogeropoulos, Sep 13 2021 *)

Prog

(PARI) A347788(n) = if(n<2, 1, !isprime(n)+sum(k=1, n-1, !(isprime(k)+isprime(n-k)))); \\ Antti Karttunen, Nov 25 2022

Crossrefs

Cf. A005171, A018252, A052284, A076608, A347796, A347797, A347798, A347799, A358638.

Sequence in context: A241701 A347662 A060177 * A238212 A255723 A309022

Adjacent sequences: A347785 A347786 A347787 * A347789 A347790 A347791

Keyword

nonn

Author

Ilya Gutkovskiy, Sep 13 2021

Status

approved