A309676 Number of compositions (ordered partitions) of n into odd primes (including 1).

1, 1, 1, 2, 3, 5, 8, 13, 21, 33, 53, 86, 138, 222, 357, 573, 921, 1481, 2381, 3828, 6153, 9890, 15898, 25556, 41082, 66039, 106156, 170644, 274307, 440945, 708815, 1139412, 1831589, 2944253, 4732847, 7607989, 12229743, 19659153, 31601828, 50799517, 81659549

Offset: 0

Author

Ilya Gutkovskiy, Aug 12 2019

Keywords

• nonn

Links

• Index entries for sequences related to compositions

Crossrefs

Cf. A002124, A006005, A008578, A023360, A080545, A280917, A298603, A298604.

Programs

Maple

a:= proc(n) option remember; `if`(n=0, 1, a(n-1)+
      add(`if`(isprime(j), a(n-j), 0), j=3..n))
    end:
seq(a(n), n=0..42);  # Alois P. Heinz, Aug 12 2019

Mathematica

nmax = 42; CoefficientList[Series[1/(1 - x - Sum[x^Prime[k], {k, 2, nmax}]), {x, 0, nmax}], x]
a[0] = 1; a[n_] := a[n] = Sum[Boole[PrimeOmega[k] < 2 && OddQ[k]] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 42}]

Formula

G.f.: 1/(1 - x - Sum_{k>=2} x^prime(k)).