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Given any \(n \in \mathbb{Z}_{\geq 0}\) and \(k \in [0,2n]\), we have \(|\{S : (S \subseteq [0,n]) \land (k \not \in S+S)\}| = 2^{|n-k|} \cdot 3^{\lfloor ((n+1)-|n-k|)/2 \rfloor}\).   Nov 17 2021

Given any \(d \in \mathbb{Z}_{\geq 1}\) and \(n=2d^2-d\), we have \(\min \{ k : \exists A \exists B : (|A|=|B|=k) \land (A,B \subseteq [0,n]) \land (A+B = [0,2n]) \} = 2d\).   Dec 13 2021

Given any \(d \in \mathbb{Z}_{\geq 1}\) and \(n=d^2-1\), we have \(\min \{ k : \exists A \exists B : (|A|=|B|=k) \land (A,B \subseteq [0,n]) \land (A+B \supseteq [0,n]) \} = d\).   Dec 13 2021

Given any \(t \in \mathbb{Z}_{\geq 1}\), \(d=2^t\), and \(n=d^2-(t-1)d-2\), we have \(\min \{ k : \exists A \exists B : (|A|=|B|=k) \land (A,B \subseteq [0,n]) \land (A+_{\leq}B \supseteq [0,n]) \} = d\).   Jan 08 2022

Given any \(m \in \mathbb{Z}_{\geq 2}\) and \(k_1, k_2 \in [0,m-1]\) with \(k_1 \not = k_2\) and \(\gcd(k_2 - k_1, m) = 1\), we have \(|\{S : (S \subseteq \mathbb{Z}_{m}) \land (k_1, k_2 \not \in S+S)\}| = F(m)\).   Oct 29 2023

Given any \(m \in \mathbb{Z}_{\geq 0}\) and \(S \subseteq \mathbb{Z}_m\), if \(|S| \geq \lfloor m / 2 \rfloor + 1\), then \(S + S = S - S = \mathbb{Z}_m\).   Nov 01 2023

Given any \(m \in \mathbb{Z}_{\geq 2}\) and \(k \in [1,m-1]\), we have \(|\{S : (S \subseteq \mathbb{Z}_{m}) \land (k \not \in S-S)\}| = L(m / \gcd(k,m))^{\gcd(k,m)}\).   Nov 03 2023

Given any \(m \in \mathbb{Z}_{\geq 1}\) and \(k \in \mathbb{Z}_{m}\), we have \(|\{S : (S \subseteq \mathbb{Z}_{m}) \land (k \not \in S+S)\}| = 3^{\lfloor (m-1) / 2 \rfloor}\).   Nov 03 2023

Conjectures

Given any \(d \in \mathbb{Z}_{\geq 2}\) and \(k=2d-2\), we have \(\max \{ n : \exists f : (f : \mathbb{Z}_{\geq 0} \to \mathbb{Z}_{\geq 0}) \land ((i \in \mathbb{Z}_{\geq 0}) \rightarrow (f(i+2) - f(i+1) \geq f(i+1) - f(i) \geq 1)) \land (S = \{f(j) : j \in [0,k-1]\}) \land (S+S \supseteq [0,n]) \} = d^2 - 2\).   Nov 26 2023

OEIS

A108411 -- comment   Oct 05 2021
A137742 -- formula   Dec 09 2021
A309407 -- formula   Jan 17 2022
A000384 -- comment   Mar 09 2022
A000290 -- comment   Mar 09 2022
A014616 -- formula   Apr 28 2022
A000217 -- comment   May 04 2022
A167809 -- comment   May 16 2022
A066062 -- formula   Oct 15 2023
A191701 -- formula   Oct 27 2023
A196021 -- formula   Oct 27 2023

Notation

\([i,j]\) denotes the integer interval \(\{i,...,j\}\), or \(\{x \in \mathbb{Z} : i \leq x \leq j\}\), where \(i,j \in \mathbb{Z}\).
\(A+B\) denotes the sumset of \(A\) and \(B\), or \(\{a+b : (a \in A) \land (b \in B)\}\).
\(A+_{\leq}B\) denotes a partial sumset of \(A\) and \(B\), specifically, \(\{a+b : (a \in A) \land (b \in B) \land (a \leq b)\}\).
\(A-B\) denotes the difference set of \(A\) and \(B\), or \(\{a-b : (a \in A) \land (b \in B)\}\).
\(F\), the sequence of Fibonacci numbers, is given by \(F(j) = F(j-1) + F(j-2)\), with \(F(0) = 0\) and \(F(1) = 1\).
\(L\), the sequence of Lucas numbers, is given by \(L(j) = L(j-1) + L(j-2)\), with \(L(2) = 3\) and \(L(3) = 4\).

Keywords

finite additive 2-basis,
sumset,
additive basis,
additive combinatorics,
combinatorial number theory,
additive number theory,
integer interval,
additive doubling,
set,
subset,
superset,
cardinality,
element,
exponential function,
floor function,
nonnegative integer,
absolute value,
minimal,
optimal,
combinatorial covering problem

Afterwards

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