cp's OEIS Frontend

A080725 a(1) = 2; for n>1, a(n) is taken to be the smallest positive integer greater than a(n-1) which is consistent with the condition "n is a member of the sequence if and only if a(n) == 1 mod 3".

%I A080725 #12 Mar 30 2012 17:27:40
%S A080725 2,4,5,7,10,11,13,14,15,16,19,20,22,25,28,31,32,33,34,37,38,40,41,42,
%T A080725 43,44,45,46,47,48,49,52,55,58,59,60,61,64,65,67,70,73,76,79,82,85,88,
%U A080725 91,94,95,96,97,98,99,100,101,102,103,106,109,112,113,114,115,118,119,121
%N A080725 a(1) = 2; for n>1, a(n) is taken to be the smallest positive integer greater than a(n-1) which is consistent with the condition "n is a member of the sequence if and only if a(n) == 1 mod 3".
%H A080725 B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL6/Cloitre/cloitre2.html">Numerical analogues of Aronson's sequence</a>, J. Integer Seqs., Vol. 6 (2003), #03.2.2.
%H A080725 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)
%H A080725 <a href="/index/Aa#aan">Index entries for sequences of the a(a(n)) = 2n family</a>
%F A080725 a(a(n)) = 3*n+1, n >= 1.
%o A080725 (PARI) {a=2; m=[2]; for(n=2,68,print1(a,","); a=a+1; if(m[1]==n, while(a%3!=1,a++); m=if(length(m)==1,[],vecextract(m,"2..")),if(a%3==1,a++)); m=concat(m,a))}
%Y A080725 Cf. A079000, A080720, ...
%K A080725 nonn,easy
%O A080725 1,1
%A A080725 _N. J. A. Sloane_, Mar 08 2003
%E A080725 More terms and PARI code from _Klaus Brockhaus_, Mar 08 2003