cp's OEIS Frontend

A120170 a(n) = ceiling( Sum_{i=1..n-1} a(i)/5 ), a(1)=1.

%I A120170 #16 Dec 27 2023 08:09:32
%S A120170 1,1,1,1,1,1,2,2,2,3,3,4,5,6,7,8,10,12,14,17,21,25,30,36,43,52,62,74,
%T A120170 89,107,128,154,185,222,266,319,383,460,552,662,795,954,1144,1373,
%U A120170 1648,1977,2373,2847,3417,4100,4920,5904,7085,8502,10202,12243,14691,17630
%N A120170 a(n) = ceiling( Sum_{i=1..n-1} a(i)/5 ), a(1)=1.
%H A120170 G. C. Greubel, <a href="/A120170/b120170.txt">Table of n, a(n) for n = 1..1000</a>
%t A120170 f[s_] := Append[s, Ceiling[Plus @@ s/5]]; Nest[f, {1}, 57] (* _Robert G. Wilson v_, Jul 07 2006 *)
%o A120170 (SageMath)
%o A120170 @CachedFunction
%o A120170 def a(n):
%o A120170     if (n==1): return 1
%o A120170     else: return ceil(sum(a(k)/5 for k in (1..n-1)))
%o A120170 [a(n) for n in (1..60)] # _G. C. Greubel_, Aug 19 2019
%o A120170 (Magma)
%o A120170 function f(n, a, b)
%o A120170   t:=0;
%o A120170     for k in [1..n-1] do
%o A120170       t+:= a+Ceiling ((b+t)/5);
%o A120170     end for;
%o A120170   return t;
%o A120170 end function;
%o A120170 g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
%o A120170 A120170:= func< n | n eq 1 select 1 else g(n-1, 1, -4) >;
%o A120170 [A120170(n): n in [1..60]]; // _G. C. Greubel_, Dec 25 2023
%Y A120170 Cf. A011782, A073941, A072493, A112088, A120160, A120178, A120186, A120194, A120202.
%K A120170 nonn
%O A120170 1,7
%A A120170 _Graeme McRae_, Jun 10 2006
%E A120170 Edited and extended by _Robert G. Wilson v_, Jul 07 2006