A120159 - OEIS

A120159

a(n) = 15 + floor((2 + Sum_{j=1..n-1} a(j))/3).

15, 20, 27, 36, 48, 64, 85, 114, 152, 202, 270, 360, 480, 640, 853, 1137, 1516, 2022, 2696, 3594, 4792, 6390, 8520, 11360, 15146, 20195, 26927, 35902, 47870, 63826, 85102, 113469, 151292, 201723, 268964, 358618, 478158, 637544, 850058, 1133411

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OFFSET

1,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

MATHEMATICA

A120159[n_]:= A120159[n]= 15 +Quotient[2 +Sum[A120159[k], {k, n-1}], 3];

Table[A120159[n], {n, 60}] (* G. C. Greubel, Aug 31 2023 *)

PROG

(Magma)

function f(n, a, b)

t:=0;

for k in [1..n-1] do

t+:= a+Floor((b+t)/3);

end for;

return t;

end function;

g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;

A120159:= func< n | g(n, 15, 2) >;

[A120159(n): n in [1..60]]; // G. C. Greubel, Aug 31 2023

(SageMath)

@CachedFunction

def A120159(n): return 15 +(2+sum(A120159(k) for k in range(1, n)))//3

[A120159(n) for n in range(1, 61)] # G. C. Greubel, Aug 31 2023

CROSSREFS

Cf. A072493, A073941, A112088.

Sequence in context: A070222 A143321 A066860 * A163602 A074236 A086770

Adjacent sequences: A120156 A120157 A120158 * A120160 A120161 A120162

KEYWORD

nonn,easy

AUTHOR

Graeme McRae, Jun 10 2006

EXTENSIONS

Name edited by G. C. Greubel, Aug 31, 2023

STATUS

approved