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
Keywords
Links
- Antti Karttunen, Table of n, a(n) for n = 0..10000
Programs
-
Mathematica
Table[Length@Flatten[Permutations/@IntegerPartitions[n,2,Select[Range@n,!PrimeQ@#&]],1],{n,0,70}] (* Giorgos Kalogeropoulos, Sep 13 2021 *)
-
PARI
A347788(n) = if(n<2,1,!isprime(n)+sum(k=1,n-1,!(isprime(k)+isprime(n-k)))); \\ Antti Karttunen, Nov 25 2022