A157644 - OEIS

%I #10 May 13 2013 01:54:10

%S 9,18,28,37,41,45,46,56,65,75,84,88,92,93,97,107,116,126,135,139,143,

%T 144,154,163,173,182,186,190,191,195,199,203,204,208,212,216,217,218,

%U 219,229,238,248,257,261,265,266,276,285,295,304,308,312,313,317,327,336,346,355

%N Indices of 3's in A090822.

%C There is a group a(i+39) = a(i)+220 for i=1,..,39, then a group a(i+39)=a(i)+220 for i=40,...,78; these correlations become irregular later in the sequence.

%H Charles R Greathouse IV, <a href="/A157644/b157644.txt">Table of n, a(n) for n = 1..10000</a>

%t Clear[a]; reversed = {a[2] = 1, a[1] = 1}; blocs[len_] := Module[{bloc1, par, pos}, bloc1 = Take[reversed, len]; par = Partition[reversed, len]; pos = Position[par, bloc_ /; bloc != bloc1, 1, 1]; If[pos == {}, Length[par], pos[[1, 1]] - 1]]; a[n_] := a[n] = Module[{an}, an = Table[{blocs[len], len}, {len, 1, Quotient[n - 1, 2]}] // Sort // Last // First; PrependTo[reversed, an]; an]; Position[Table[a[n], {n, 1, 355}], 3] // Flatten (* _Jean-François Alcover_, Mar 25 2013 *)

%Y Cf. A157334, A107223, A157645.

%K nonn

%O 1,1

%A _Paul Curtz_, Mar 03 2009

%E Extended by _R. J. Mathar_, Mar 15 2009