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Number of ways to split an integer partition of n into contiguous subsequences with strictly increasing sums.
11

%I #11 Jan 19 2024 02:19:08

%S 1,1,2,4,6,11,17,27,37,62,82,125,168,246,320,462,585,839,1078,1466,

%T 1830,2528,3136,4188,5210,6907,8498,11177,13570,17668,21614,27580,

%U 33339,42817,51469,65083,78457,98409,117602,147106,174663,217400,259318,319076,377707

%N Number of ways to split an integer partition of n into contiguous subsequences with strictly increasing sums.

%H Andrew Howroyd, <a href="/A336134/b336134.txt">Table of n, a(n) for n = 0..75</a>

%e The a(1) = 1 through a(6) = 17 splits:

%e (1) (2) (3) (4) (5) (6)

%e (1,1) (2,1) (2,2) (3,2) (3,3)

%e (1,1,1) (3,1) (4,1) (4,2)

%e (1),(1,1) (2,1,1) (2,2,1) (5,1)

%e (1,1,1,1) (3,1,1) (2,2,2)

%e (1),(1,1,1) (2,1,1,1) (3,2,1)

%e (2),(2,1) (4,1,1)

%e (1,1,1,1,1) (2,2,1,1)

%e (2),(1,1,1) (2),(2,2)

%e (1),(1,1,1,1) (3,1,1,1)

%e (1,1),(1,1,1) (2,1,1,1,1)

%e (2),(2,1,1)

%e (1,1,1,1,1,1)

%e (2),(1,1,1,1)

%e (1),(1,1,1,1,1)

%e (1,1),(1,1,1,1)

%e (1),(1,1),(1,1,1)

%t splits[dom_]:=Append[Join@@Table[Prepend[#,Take[dom,i]]&/@splits[Drop[dom,i]],{i,Length[dom]-1}],{dom}];

%t Table[Sum[Length[Select[splits[ctn],Less@@Total/@#&]],{ctn,IntegerPartitions[n]}],{n,0,10}]

%o (PARI) a(n)={my(recurse(r,m,s,t,f)=if(m==0, r==0, if(f && r > t && t >= s, self()(r,m,t+1,0,0)) + self()(r,m-1,s,t,0) + self()(r-m,min(m,r-m), s,t+m,1))); recurse(n,n,0,0,0)} \\ _Andrew Howroyd_, Jan 18 2024

%Y The version with equal sums is A317715.

%Y The version with strictly decreasing sums is A336135.

%Y The version with weakly decreasing sums is A316245.

%Y The version with different sums is A336131.

%Y Starting with a composition gives A304961.

%Y Starting with a strict partition gives A336133.

%Y Partitions of partitions are A001970.

%Y Partitions of compositions are A075900.

%Y Compositions of compositions are A133494.

%Y Compositions of partitions are A323583.

%Y Cf. A006951, A063834, A279786, A305551, A318684, A323433, A336128, A336130.

%K nonn

%O 0,3

%A _Gus Wiseman_, Jul 11 2020

%E a(21) onwards from _Andrew Howroyd_, Jan 18 2024