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 A180352 A permutation of Motzkin numbers by reversal of indices in blocks of length 7. 1

%I

%S 127,51,21,9,4,2,1,113634,41835,15511,5798,2188,835,323,142547559,

%T 50852019,18199284,6536382,2356779,853467,310572,208023278209,

%U 73007772802,25669818476,9043402501,3192727797,1129760415,400763223

%N A permutation of Motzkin numbers by reversal of indices in blocks of length 7.

%C The sequence shows A001006(7) down to A001006(1), then A001006(14) down to A001006(8), etc, varying the index in a sawtooth pattern.

%C Comment 1: When I initially logged in to use the OEIS, it 'pre-loaded' the search box with a sequence. The seven terms 127,51,21,9,4,2,1 are obtained from that original one by reversing the terms.

%C 2. "Periodic" term reversals of this sort are routinely encountered when writing out convolution sums.

%F Let r(n) = 7, 6, 5 ,4, 3, 2, 1 (n>=1), extended with r(n+7)=7+r(n), then a(n) = A001006(r(n)).

%o (Sage) A180352 = lambda n: A001006(7*((n-1)//7+1)-((n-1) % 7)) [D. S. McNeil, Dec 6 2010]

%Y Cf. A001006, A073794

%K less,easy,nonn

%O 1,1

%A Matt Insall (insall(AT)mst.edu), Aug 29 2010

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