

A245937


Index sequence for limitreversing A000002; see Comments.


3



1, 4, 7, 16, 25, 31, 43, 61, 70, 88, 97, 115, 220, 286, 322, 475, 557, 1072, 1334, 1598, 1751, 1964, 1991, 2385, 2494, 2909, 2936, 3326, 3935, 4518, 5363, 5696, 6232, 6323, 6541, 6940, 7120, 7570, 7840, 12217, 12397, 12906, 13901, 16129, 18277, 20342, 20803
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OFFSET

1,2


COMMENTS

Suppose S = (s(0),s(1),s(2),...) is an infinite sequence such that every finite block of consecutive terms occurs infinitely many times in S. (It is assumed that A006337 is such a sequence.) Let B = B(m,k) = (s(mk),s(mk+1),...,s(m)) be such a block, where m >= 0 and k >= 0. Let m(1) be the least i > m such that (s(ik),s(ik+1),...,s(i)) = B(m,k), and put B(m(1),k+1) = (s(m(1)k1),s(m(1)k),...,s(m(1))). Let m(2) be the least i > m(1) such that (s(ik1),s(ik),...,s(i)) = B(m(1),k+1), and put B(m(2),k+2) = (s(m(2)k2),s(m(2)k1),...,s(m(2))). Continuing in this manner gives a sequence of blocks B(m(n),k+n). Let B'(n) = reverse(B(m(n),k+n)), so that for n >= 1, B'(n) comes from B'(n1) by suffixing a single term; thus the limit of B'(n) is defined; we call it the "limitreverse of S with initial block B(m,k)", denoted by S*(m,k), or simply S*. (Since A000002 has offset 1, the above definition is adapted accordingly, so that s(n) = A000002(n+1) for n >= 0.)
...
The sequence (m(i)), where m(0) = 1, is the "index sequence for limitreversing S with initial block B(m,k)" or simply the index sequence for S*, as in A245937.


LINKS

Table of n, a(n) for n=1..47.


EXAMPLE

S = A000002 (reindexed to start with s(0) = 1, with B = (s(0)); that is, (m,k) = (0,0); S = (1,2,2,1,1,2,1,2,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,,...)
B'(0) = (1)
B'(1) = (1,2)
B'(2) = (1,2,1)
B'(3) = (1,2,1,1)
B'(4) = (1,2,1,1,2)
B'(5) = (1,2,1,1,2,2)
S* = (1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1,...),
with index sequence (1, 4, 7, 16, 25, 31, 43, 61, 70, 88, 97, 115,...)


MATHEMATICA

z = 50; seqPosition2[list_, seqtofind_] := Last[Last[Position[Partition[list, Length[#], 1], Flatten[{___, #, ___}], 1, 2]]] &[seqtofind]; n = 30; s = Prepend[Nest[ Flatten[Partition[#, 2] /. {{2, 2} > {2, 2, 1, 1}, {2, 1} > {2, 2, 1}, {1, 2} > {2, 1, 1}, {1, 1} > {2, 1}}] &, {2, 2}, n], 1]; ans = Join[{s[[p[0] = pos = seqPosition2[s, #]  1]]}, #] &[{s[[1]]}]; cfs = Table[s = Drop[s, pos  1]; ans = Join[{s[[p[n] = pos = seqPosition2[s, #]  1]]}, #] &[ans], {n, z}]; q = Accumulate[Join[{1}, Table[p[n], {n, 0, z}]]] (* A245937 *)


CROSSREFS

Cf. A000002, A245936, A245920.
Sequence in context: A285998 A229917 A095755 * A259653 A164123 A005513
Adjacent sequences: A245934 A245935 A245936 * A245938 A245939 A245940


KEYWORD

nonn


AUTHOR

Clark Kimberling and Peter J. C. Moses, Aug 07 2014


STATUS

approved



