

A180352


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


1



127, 51, 21, 9, 4, 2, 1, 113634, 41835, 15511, 5798, 2188, 835, 323, 142547559, 50852019, 18199284, 6536382, 2356779, 853467, 310572, 208023278209, 73007772802, 25669818476, 9043402501, 3192727797, 1129760415, 400763223
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

The sequence shows A001006(7) down to A001006(1), then A001006(14) down to A001006(8), etc., varying the index in a sawtooth pattern.
When I initially logged in to use the OEIS, it 'preloaded' 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.
"Periodic" term reversals of this sort are routinely encountered when writing out convolution sums.


LINKS

Table of n, a(n) for n=1..28.


FORMULA

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)).


PROG

(Sage) A180352 = lambda n: A001006(7*((n1)//7+1)((n1) % 7)) # D. S. McNeil, Dec 06 2010


CROSSREFS

Cf. A001006, A073794
Sequence in context: A051335 A186995 A145586 * A217557 A320571 A082456
Adjacent sequences: A180349 A180350 A180351 * A180353 A180354 A180355


KEYWORD

less,easy,nonn


AUTHOR

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


STATUS

approved



