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# User:Charles R Greathouse IV/Projects

There are a number of mathematical projects, sites, or programs ("projects" for short) which are similar to (at least one aspect of) the OEIS. This page is an attempt to describe and list some of these projects.

## Properties

Billey & Tenner's[1] Fingerprint databases for theorems is a key resource. They suggest that the purpose of projects is to encode theorems with a fingerprint satisfying these conditions:

• Should be language independent.
• Should reference existing literature.
• Should be collaborative and publicly available.
• Should be encoded in a small amount of data.

## List of projects

### On-Line Encyclopedia of Integer Sequences

This is Billey & Tenner's prime example of a fingerprint database for theorems, listed here only for completeness.

### Database of Permutation Pattern Avoidance

A database of permutations which avoid a finite number of permutation patterns. Permutations can be searched by a subset of the avoided patterns and/or by keyword. Contains 54 entries as of Oct 2018. Data for each entry includes the avoided pattern(s), a title, references, the enumeration (a name, formula, or generating function), an OEIS reference for the enumeration, and the contributor.

### The Combinatorial Statistic Finder

Finds combinatorial statistics. Different types of search are available based on the type of statistic searched for (out of these 17):

• Alternating sign matrices; binary trees; cores; Dyck paths; finite Cartan types; Gelfand-Tsetlin patterns; graphs; integer compositions; integer partitions; ordered trees; parking functions; perfect matchings; permutations; posets; semistandard tableaux; set partitions; standard tableaux

As of Oct 2018 there were 1278 statistics in the database. Data for each statistic includes values, description, code, references, and author.

### Hypergeometric series / WZ method / A = B

A method for finding hypergeometric identities or proving their nonexistence. Software support exists in Maple and Mathematica.

### House of Graphs

A searchable database of interesting graphs developed by G. Brinkmann, J. Goedgebeur, H. Mélot and K. Coolsaet.

The database allows searches by text and any of these 23 graph invariants:

• Acyclic?; algebraic connectivity; average degree; bipartite?; chromatic index; chromatic number; claw-free?; clique number; connected?; diameter; edge connectivity; Eulerian?; genus; girth; Hamiltonian?; independence number; index; Laplacian largest eigenvalue; longest induced cycle; longest induced path; matching number; maximum degree; minimum degree; minimum dominating set; number of components; number of edges; number of triangles; number of vertices; radius; regular?; second largest eigenvalue; smallest eigenvalue; vertex connectivity

with a given value or in a given interval (except the binary properties, marked with a ? in this list, which can be only present or absent).

Further, graphs can be drawn or uploaded (using any of their 6 supported formats).

As of Oct 2018 the database contained 13,896 graphs.

• House of Graphs
• Gunnar Brinkmann, Kris Coolsaet, Jan Goedgebeur, and Hadrien Melot, House of Graphs: a database of interesting graphs (2012). arXiv:1204.3549 (math.CO; cs.DM)
• G. Brinkmann, K. Coolsaet, J. Goedgebeur, H. Mélot, House of Graphs: a database of interesting graphs, Discrete Applied Mathematics, 161:311-314, 2013 (DOI). Available at http://hog.grinvin.org

### RIES

Robert Munafo's tool to "find algebraic equations, given their solution". Uses a bidirectional search to find candidates of length n in time Õ(2n/2). Available online or for download (C source).

### Inverse Symbolic Calculator

Simon Plouffe's tool for detecting real numbers appearing in various forms. Apparently a private form also exists, which can be queried by request to Simon Plouffe via email.

### gfun

Algorithmic detection of generating functions from Maple. Written by Bruno Salvy and Paul Zimmermann.

### SequenceBoss

A relatively new (2015) project by Philipp Emanuel Weidmann. Accepts sequence queries.

### Groupprops

Vipul Naik's brainchild, a wiki with 7000+ pages collecting information on the properties of various groups, especially finite groups. The project dates back to 2006 (2008 in its present form). Data includes presence or absence of common group properties, membership in various families, morphisms, and conjugacy class structure. GAP code is often included. Text searches are the primary way to find pages, though there is a query creator which allows searching by category as well.

### Integer Sequences

Tony D. Noe's collection of about a thousand integer sequences, started in 2014. Includes formulas, graphs, Mathematica programs, and references (but unfortunately no search features). Text is apparently freeform; metadata consists of OEIS-inspired keywords: base, cons, fini, full, hard, more, nice, nonn, sign, tabf, tabl. Entries are crosslinked with other entries and also with OEIS entries.

### The Number Fields Database

John Jones and David Roberts

An extension of an older project by John Jones at [1].

### A Database for Number Fields

A collection of transitive groups by degree, created by Jürgen Klüners and Gunter Malle in 2001.

### L-functions and modular forms database

The L-functions and modular forms database (LMFDB) collects number-theoretical objects such as L-functions, L-function zeros, elliptic curves, Maass forms, and number fields.

### π-Base

James Dabbs' collections of counterexamples in topology. As of January 2016 it contains 159 spaces, 94 properties, and 214 theorems. It allows complex Boolean queries and is designed for automated deduction. Work goes back to at least 2013.

### Reverse Mathematics Zoo

A database of reverse mathematical implications, conservation facts, and reducibilities, especially in the big five subsystems of second order arithmetic: RCA0, WKL0, ACA0, ATR0, and Π${\displaystyle \scriptstyle _{1}^{1}}$-CA0. It was developed Damir Dzhafarov and has been recently rewritten by Eric Astor.

### Sequence Database

"A database with 1693109 machine generated integer and decimal sequences." (as of Oct 29 2018) Contains sequence tags, function tags, OEIS references, and attempts at combining identical sequences with different definitions.

### Encyclopedia of Delay-Insensitive Systems (EDIS)

Delay-insensitive systems operate correctly regardless of delays in components and connections. For each entry, information may include

1. Specifications, both informal and in various formalisms (XDI Model, VERDECT, DI Algebra).
2. Properties, such as symmetries (structural and behavioral automorphisms), classifications (kind of choice or nondeterminism involved), independent environments, etc.
3. Implementations, DI decompositions, and gate and/or transistor designs where relevant
4. Generalizations
5. Miscellaneous, such as associated problems and conjectures, historic notes, etc.
6. References

It appears to contain several dozen entries and has a last-modified date of 1998.

## Notes

1. Sara C. Billey; Bridget E. Tenner. “Fingerprint databases for theorems”. Notices of the AMS 60 (8): pp. 1034–1039. arXiv:1304.3866.