A081260 - OEIS

A081260

a(1)=4; for n>1, a(n) is taken to be the third-smallest integer greater than a(n-1) such that the condition "n is a member of the sequence if and only if a(n) is odd" is satisfied.

%I #5 Mar 30 2012 17:27:18

%S 4,10,16,21,26,32,38,44,50,55,60,66,72,78,84,89,94,100,106,112,117,

%T 122,128,134,140,145,150,156,162,168,174,179,184,190,196,202,208,213,

%U 218,224,230,236,242,247,252,258,264,270,276,281,286,292,298,304,309,314

%N a(1)=4; for n>1, a(n) is taken to be the third-smallest integer greater than a(n-1) such that the condition "n is a member of the sequence if and only if a(n) is odd" is satisfied.

%H B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://www.cs.uwaterloo.ca/journals/JIS/index.html">Numerical analogues of Aronson's sequence</a>, J. Integer Seqs., Vol. 6 (2003), #03.2.2.

%H B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://arXiv.org/abs/math.NT/0305308">Numerical analogues of Aronson's sequence</a> (math.NT/0305308)

%e a(1)=4, implying that the fourth term is the first odd member of the sequence; hence a(2) and a(3) are even. The third-smallest even integer greater than 4 is 10; therefore a(2)=10. The third-smallest integers that can satisfy the given condition if taken as a(3) and a(4) are 16 and 21, respectively.

%Y Cf. A079000, A080753.

%K easy,nonn

%O 1,1

%A _Matthew Vandermast_, Mar 14 2003