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%I #8 Mar 03 2016 15:31:01
%S 1,4,7,9,12,15,18,21,23,26,29,31,34,37,39,42,45,47,50,53,56,59,61,64,
%T 67,69,72,75,78,81,83,86,89,91,94,97,100,103,105,108,111,113,116,119,
%U 122,125,127,130,133,135,138,141,143,146,149,151,154,157
%N a(1)=1, a(n)=a(n-1)+2 if (n and n+3 are in the sequence), a(n)=a(n-1)+3 otherwise.
%H Ivan Neretin, <a href="/A080902/b080902.txt">Table of n, a(n) for n = 1..1000</a>
%F Conjectured to be asymptotic to r*n, where r=2.72... Is r the largest root of q^2-3*q+3/4, which is 2.72474487139...?
%e a(9)=a(8)+2 since 9 and 12 are in the sequence.
%t Fold[Append[#1, #1[[-1]] + If[MemberQ[#1, #2] && MemberQ[#1, #2 + 3], 2, 3]] &, {1}, Range[2, 58]] (* _Ivan Neretin_, Mar 03 2016 *)
%K nonn
%O 1,2
%A _Benoit Cloitre_, Apr 01 2003
%E Corrected by _T. D. Noe_, Nov 02 2006
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