A347739 Number of compositions (ordered partitions) of n into at most 2 prime parts.

1, 0, 1, 1, 1, 3, 1, 3, 2, 2, 3, 1, 2, 3, 3, 2, 4, 1, 4, 3, 4, 2, 5, 1, 6, 2, 5, 0, 4, 1, 6, 3, 4, 2, 7, 0, 8, 1, 3, 2, 6, 1, 8, 3, 6, 2, 7, 1, 10, 2, 8, 0, 6, 1, 10, 2, 6, 0, 7, 1, 12, 3, 5, 2, 10, 0, 12, 1, 4, 2, 10, 1, 12, 3, 9, 2, 10, 0, 14, 1, 8

Offset

0,6

Links

Table of n, a(n) for n=0..80.

Formula

a(n) = Sum_{k=1..2} A121303(n,k) for n >= 2. - Alois P. Heinz, Sep 11 2021

Mathematica

Table[Length@Flatten[Permutations/@IntegerPartitions[n, 2, Prime@Range@PrimePi@n], 1], {n, 0, 100}] (* Giorgos Kalogeropoulos, Sep 12 2021 *)

Crossrefs

Cf. A000040, A023360, A073610, A121303, A347740, A347741, A347742, A347743.

Sequence in context: A171899 A355784 A213885 * A352931 A083208 A367454

Adjacent sequences: A347736 A347737 A347738 * A347740 A347741 A347742

Keyword

nonn

Author

Ilya Gutkovskiy, Sep 11 2021

Status

approved