notebook/notes/combinatorics/index.md

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title TARGET DECK FILE TAGS tags
Combinatorics Obsidian::STEM combinatorics set
combinatorics
set

Overview

When selecting objects, we can use the given table to hint at what counting strategy we should use:

Order Repeats Answer Shape Reference
Yes Yes n^k -
Yes No (n)_k permutations#Falling Factorials
No Yes \binom{n + k}{k} combinations#Stars and Bars
No No \binom{n}{k} combinations

%%ANKI Basic What does it mean for order to matter? Back: We get different outcomes if the same objects are selected in different orders. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic What does it mean for repeats to be allowed? Back: The same object can be selected multiple times. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic What combinatorial notation corresponds to the highlighted square? !ordering-y-repetition-y.jpg Back: n^k Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic What combinatorial concept corresponds to the highlighted square? !ordering-y-repetition-y.jpg Back: The multiplicative principle. Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic Which square corresponds to notation n^k? !ordering-repetition.jpg Back: !ordering-y-repetition-y.jpg

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%%ANKI Basic What combinatorial notation corresponds to the highlighted square? !ordering-y-repetition-n.jpg Back: (n)_k Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic What combinatorial concept corresponds to the highlighted square? !ordering-y-repetition-n.jpg Back: k-permutations (falling factorials) Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic Which square corresponds to notation (n)_k? !ordering-repetition.jpg Back: !ordering-y-repetition-n.jpg

END%%

%%ANKI Basic What combinatorial notation corresponds to the highlighted square? !ordering-n-repetition-y.jpg Back: \binom{n + k}{k} Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

END%%

%%ANKI Basic What combinatorial concept corresponds to the highlighted square? !ordering-n-repetition-y.jpg Back: Stars and bars Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

END%%

%%ANKI Basic Which square corresponds to notation \binom{n + k}{k}? !ordering-repetition.jpg Back: !ordering-n-repetition-y.jpg

END%%

%%ANKI Basic What combinatorial notation corresponds to the highlighted square? !ordering-n-repetition-n.jpg Back: \binom{n}{k} Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

END%%

%%ANKI Basic What combinatorial concept corresponds to the highlighted square? !ordering-n-repetition-n.jpg Back: Combinations Reference: Oscar Levin, Discrete Mathematics: An Open Introduction, 3rd ed., n.d., https://discrete.openmathbooks.org/pdfs/dmoi3-tablet.pdf.

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%%ANKI Basic Which square corresponds to notation \binom{n}{k}? !ordering-repetition.jpg Back: !ordering-n-repetition-n.jpg

END%%

Bibliography