A348401 - OEIS

%I #8 Oct 19 2021 09:31:51

%S 1,2,3,4,5,3,7,8,9,10,11,4,13,14,15,16,17,18,19,5,21,22,23,4,25,26,27,

%T 28,29,6,31,32,33,34,35,36,37,38,39,40,41,7,43,44,45,46,47,48,49,50,

%U 51,52,53,54,55,8,57,58,59,5,61,62,63,64,65,66,67,68,69

%N a(n) is the least m > 0 such that n = m! / k! for some k <= m.

%C For any n > 0, n appears in the a(n)-th row of A346928.

%H Rémy Sigrist, <a href="/A348401/a348401.gp.txt">PARI program for A348401</a>

%F a(n) <= n.

%F a(n) < n iff n belongs to A045619 \ {2}.

%F If n = A045619(k), then a(n) = A137912(k). - _R. J. Mathar_, Oct 19 2021

%o (PARI) See Links section.

%o (Python)

%o from math import factorial

%o def a(n):

%o     f = [factorial(i) for i in range(1, n+1)]

%o     for m, fm in enumerate(f, start=1):

%o         for fk in f[:m]:

%o             if n == fm // fk:

%o                 return m

%o print([a(n) for n in range(1, 70)]) # _Michael S. Branicky_, Oct 17 2021

%Y Cf. A045619, A346928.

%K nonn

%O 1,2

%A _Rémy Sigrist_, Oct 17 2021