

A130766


3n+2 sandwiched by tripled 3n+1 .


1



1, 1, 1, 2, 4, 4, 4, 5, 7, 7, 7, 8, 10, 10, 10, 11, 13, 13, 13, 14, 16, 16, 16, 17, 19, 19, 19, 20, 22, 22, 22, 23, 25, 25, 25, 26, 28, 28, 28, 29, 31, 31, 31, 32, 34, 34, 34, 35, 37, 37, 37, 38, 40, 40, 40, 41, 43, 43, 43, 44, 46, 46, 46, 47, 49, 49, 49, 50, 52, 52, 52, 53, 55
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OFFSET

0,4


LINKS



FORMULA

a(n) = a(n1) + a(n4)  a(n5) for n > 4.
G.f.: (x^4 + x^3 + 1)/(x^5  x^4  x + 1). (End)
a(n) = 2*floor(n/4) + floor((n+1)/4) + 1.  Ridouane Oudra, Jan 26 2024


MATHEMATICA

CoefficientList[Series[(x^4 + x^3 + 1) / (x^5  x^4  x + 1), {x, 0, 100}], x] (* Vincenzo Librandi, Jun 18 2016 *)
LinearRecurrence[{1, 0, 0, 1, 1}, {1, 1, 1, 2, 4}, 100] (* Harvey P. Dale, Apr 18 2023 *)


PROG

(Magma) I:=[1, 1, 1, 2, 4]; [n le 5 select I[n] else Self(n1)+Self(n4)Self(n5): n in [1..80]]; // Vincenzo Librandi, Jun 18 2016


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



