cp's OEIS Frontend

A348401 a(n) is the least m > 0 such that n = m! / k! for some k <= m.

%I A348401 #8 Oct 19 2021 09:31:51
%S A348401 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 A348401 28,29,6,31,32,33,34,35,36,37,38,39,40,41,7,43,44,45,46,47,48,49,50,
%U A348401 51,52,53,54,55,8,57,58,59,5,61,62,63,64,65,66,67,68,69
%N A348401 a(n) is the least m > 0 such that n = m! / k! for some k <= m.
%C A348401 For any n > 0, n appears in the a(n)-th row of A346928.
%H A348401 Rémy Sigrist, <a href="/A348401/a348401.gp.txt">PARI program for A348401</a>
%F A348401 a(n) <= n.
%F A348401 a(n) < n iff n belongs to A045619 \ {2}.
%F A348401 If n = A045619(k), then a(n) = A137912(k). - _R. J. Mathar_, Oct 19 2021
%o A348401 (PARI) See Links section.
%o A348401 (Python)
%o A348401 from math import factorial
%o A348401 def a(n):
%o A348401     f = [factorial(i) for i in range(1, n+1)]
%o A348401     for m, fm in enumerate(f, start=1):
%o A348401         for fk in f[:m]:
%o A348401             if n == fm // fk:
%o A348401                 return m
%o A348401 print([a(n) for n in range(1, 70)]) # _Michael S. Branicky_, Oct 17 2021
%Y A348401 Cf. A045619, A346928.
%K A348401 nonn
%O A348401 1,2
%A A348401 _Rémy Sigrist_, Oct 17 2021