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 A322880 Number of set partitions of [n] such that the maximal absolute difference between the least elements of consecutive blocks equals seven. 2

%I

%S 0,1,67,1059,11373,106256,940608,8193031,71568443,633413486,

%T 5710573774,52579554510,494986212033,4766754646529,46966622143740,

%U 473477764449909,4883216510830794,51513192445470426,555667122424414886,6127026713823497897,69034256792655555566

%N Number of set partitions of [n] such that the maximal absolute difference between the least elements of consecutive blocks equals seven.

%H Alois P. Heinz, <a href="/A322880/b322880.txt">Table of n, a(n) for n = 7..580</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Partition_of_a_set">Partition of a set</a>

%F a(n) = A287257(n) - A287256(n).

%p b:= proc(n, k, m, l) option remember; `if`(n<1, 1,

%p `if`(l-n>k, 0, b(n-1, k, m+1, n))+m*b(n-1, k, m, l))

%p end:

%p A:= (n, k)-> b(n-1, min(k, n-1), 1, n):

%p a:= n-> (k-> A(n, k)-A(n, k-1))(7):

%p seq(a(n), n=7..30);

%Y Column k=7 of A287215.

%Y Cf. A287256, A287257.

%K nonn

%O 7,3

%A _Alois P. Heinz_, Dec 29 2018

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Last modified August 11 01:53 EDT 2020. Contains 336418 sequences. (Running on oeis4.)