

A225875


We write the 1 + 4*k numbers once and twice the others.


0



1, 2, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 8, 8, 9, 10, 10, 11, 11, 12, 12, 13, 14, 14, 15, 15, 16, 16, 17, 18, 18, 19, 19, 20, 20, 21, 22, 22, 23, 23, 24, 24, 25, 26, 26, 27, 27, 28, 28, 29, 30, 30, 31, 31, 32, 32, 33, 34, 34, 35, 35, 36, 36, 37, 38, 38, 39, 39, 40, 40, 41, 42, 42, 43
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OFFSET

1,2


COMMENTS

First differences are periodic with period 7.


LINKS

Table of n, a(n) for n=1..74.
Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 1, 1).


FORMULA

a(n+1) = 1 + 4*floor(n/7) + [0,1,1,2,2,3,3].
G.f.: x*(1 + x + x^3 + x^5)/((1x)^2 * (1 + x + x^2 + x^3 + x^4 + x^5 + x^6)).
a(n) = n  floor(3*n/7).  Wesley Ivan Hurt, Sep 29 2017


MATHEMATICA

t = {}; Do[If[Mod[n, 4] == 1, AppendTo[t, n], AppendTo[t, {n, n}]], {n, 50}]; Flatten[t] (* T. D. Noe, May 23 2013 *)
LinearRecurrence[{1, 0, 0, 0, 0, 0, 1, 1}, {1, 2, 2, 3, 3, 4, 4, 5}, 74] (* Ray Chandler, Aug 26 2015 *)
Table[If[Mod[n, 4] == 1, n, {n, n}], {n, 50}] // Flatten (* or *) Drop[ Flatten[ Table[{n, n}, {n, 50}]], {1, 1, 8}] (* Harvey P. Dale, Feb 03 2019 *)


CROSSREFS

Cf. A132270.
Sequence in context: A100679 A226190 A195182 * A189688 A092982 A302930
Adjacent sequences: A225872 A225873 A225874 * A225876 A225877 A225878


KEYWORD

nonn,easy


AUTHOR

José María Grau Ribas, May 19 2013


EXTENSIONS

Corrected, extended, and edited by Ralf Stephan, May 20 2013


STATUS

approved



