

A026185


If n even, then 2n. If n odd, then nearest integer to 2n/3.


5



0, 1, 4, 2, 8, 3, 12, 5, 16, 6, 20, 7, 24, 9, 28, 10, 32, 11, 36, 13, 40, 14, 44, 15, 48, 17, 52, 18, 56, 19, 60, 21, 64, 22, 68, 23, 72, 25, 76, 26, 80, 27, 84, 29, 88, 30, 92, 31, 96, 33, 100, 34, 104, 35, 108, 37, 112, 38, 116, 39, 120, 41
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OFFSET

0,3


COMMENTS

For n > 0, position of n in A026184. In other words, this is the inverse permutation to A026184. For proof, see the Reble link.
Permutation of nonnegative integers: lodumo_4 of (0,1,0,2,0,3,0,1,0,2,0,3,0,1,0,2,0,3,0,1,0,2,0,3,0,1,0,2,0,3,...).  Philippe Deléham, Oct 25 2011


LINKS



FORMULA

a(2n)=4n; a(6n+1)=4n+1; a(6n+3)=4n+2; a(6n+5)=4n+3. G.f.: x(1+4*x+x^2+4*x^3+x^4+4*x^5+x^6)/((1+x^2+x^4)*(1x^2)^2).  Philippe Deléham, Oct 25 2011


MATHEMATICA

Table[If[EvenQ[n], 2 n, Round[2 n/3]], {n, 0, 50}] (* Vincenzo Librandi, Feb 03 2020 *)


PROG

(Magma) [IsEven(n) select 2*n else Round(2*n/3): n in [0..79] ]; // Vincenzo Librandi, Feb 03 2020


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS

Edited by N. J. A. Sloane, Feb 02 2020, changing the definition to one given by Philippe Deléham, Oct 25 2011, and making the old definition a comment. Thanks to Don Reble for proving that the two definitions produce the same sequence.


STATUS

approved



