This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A180352 #8 Mar 13 2014 02:50:49 %S A180352 127,51,21,9,4,2,1,113634,41835,15511,5798,2188,835,323,142547559, %T A180352 50852019,18199284,6536382,2356779,853467,310572,208023278209, %U A180352 73007772802,25669818476,9043402501,3192727797,1129760415,400763223 %N A180352 A permutation of Motzkin numbers by reversal of indices in blocks of length 7. %C A180352 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 A180352 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 A180352 "Periodic" term reversals of this sort are routinely encountered when writing out convolution sums. %F A180352 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 A180352 (Sage) A180352 = lambda n: A001006(7*((n-1)//7+1)-((n-1) % 7)) # _D. S. McNeil_, Dec 06 2010 %Y A180352 Cf. A001006, A073794 %K A180352 less,easy,nonn %O A180352 1,1 %A A180352 Matt Insall (insall(AT)mst.edu), Aug 29 2010