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A072493 a(1)=1, a(n) = ceiling((Sum_{k=1..n-1} a(k))/3). 82
1, 1, 1, 1, 2, 2, 3, 4, 5, 7, 9, 12, 16, 22, 29, 39, 52, 69, 92, 123, 164, 218, 291, 388, 517, 690, 920, 1226, 1635, 2180, 2907, 3876, 5168, 6890, 9187, 12249, 16332, 21776, 29035, 38713, 51618, 68824, 91765, 122353, 163138, 217517, 290023, 386697 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Is this sequence, with its first 8 terms removed, the same as A005427? See also the similar conjecture with A005428/A073941. - Ralf Stephan, Apr 04 2003

Yes; the first 8 terms sum to 15, so upon dividing by 3 they are equivalent to the +5 in the formula for A005427. - Charlie Neder, Jan 10 2019

LINKS

Michel Marcus, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = ceiling(c*(4/3)^n-1/2) where c=0.389324199524937508840138455...

MATHEMATICA

f[s_] := Append[s, Ceiling[Plus @@ s/3]]; Nest[f, {1}, 52] (* Robert G. Wilson v, Jul 07 2006 *)

PROG

(PARI) lista(nn) = {va = vector(nn); va[1] = 1; for (n=2, nn, va[n] = ceil(sum(k=1, n-1, va[k])/3); ); va; } \\ Michel Marcus, Apr 16 2015

CROSSREFS

Cf. A073941, A005427, A005428.

Sequence in context: A182097 A290697 A290821 * A064324 A173090 A032277

Adjacent sequences:  A072490 A072491 A072492 * A072494 A072495 A072496

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Nov 22 2002

STATUS

approved

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Last modified December 12 07:31 EST 2019. Contains 329948 sequences. (Running on oeis4.)