A120173 a(n) = 4 + floor((3 + Sum_{j=1..n-1} a(j))/5).

4, 5, 6, 7, 9, 10, 12, 15, 18, 21, 26, 31, 37, 44, 53, 64, 77, 92, 110, 132, 159, 191, 229, 275, 330, 396, 475, 570, 684, 821, 985, 1182, 1418, 1702, 2042, 2451, 2941, 3529, 4235, 5082

Offset: 1

Author

Graeme McRae, Jun 10 2006

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A073941, A072493, A112088.

Programs

Magma

function f(n, a, b)
  t:=0;
    for k in [1..n-1] do
      t+:= a+Floor((b+t)/5);
    end for;
  return t;
end function;
g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
A120173:= func< n | g(n, 4, 3) >;
[A120173(n): n in [1..60]]; // G. C. Greubel, Dec 26 2023

Mathematica

A120173[n_]:= A120173[n]= 4 +Floor[(3 +Sum[a[j], {j,n-1}])/5];
Table[A120173[n], {n, 60}] (* G. C. Greubel, Dec 26 2023 *)

SageMath

@CachedFunction
def f(n, p, q): return p + (q +sum(f(k, p, q) for k in range(1, n)))//5
def A120173(n): return f(n, 4, 3)
[A120173(n) for n in range(1, 61)] # G. C. Greubel, Dec 26 2023