More continued fractions and constants

[itaybthl]

The database can always benefit from more values added, from relevant collections of constants. The sources we are currently interested in, in decreasing order of priority, are:

1. All remaining Ramanujan Machine publications, which are:
   1. Automated Search for Conjectures on Mathematical Constants using Analysis of Integer Sequences (alias razon). SICFs should be uploaded as PCFs by using the folding transform (probably better to just use pcf_from_matrix though)
   2. On Euler polynomial continued fraction (alias epcf).
   3. The conservative matrix field (alias cmf).
   4. Algorithm-assisted discovery of an intrinsic order among mathematical constants (alias elimelech).
2. More wikipedia articles, including:
   1. Generalized continued fraction (alias wikipedia gcf).
   2. Contiuned fraction (alias wikipedia cf), Only add continued fractions whose partial numerator and denominator are polynomials, or cyclic sequences of polynomials.
3. OEIS (alias oeis). Specifically, all sequences with the cons keyword represent the digits of some constant, usually in base 10. We suggest using this page for downloading all sequences and filtering them.
4. Handbook of Continued Fractions for Special Functions by Annie Cuyt et al. (alias cuyt).

The guidelines for uploading constants are:

• Every value's precision must be at most 16000 digits of precision, even if more digits are known or easy to compute. This includes both the precision field and the amount of digits in the value field.
• Any named constant that is not computable must not be uploaded.
• Any named constant whose known precision is less than 50 may be uploaded, but its value must remain null.
• PCFs must be computed to depths that are a power of $2$, up to a depth of $2^{20}$. (The previous rule does NOT apply here! if a PCF converges so slow that 50 digits aren't achievable even after a depth of $2^{20}$, upload it as is!)
• To compute a PCF, start by converting it to its canonical form, then return to a PCF from the canonical form. Do not directly compute any PCF without doing this first.
• When adding sources to constants, respect the existing sources, and prioritize crediting the highest-priority source. When beginning to scour a source, add it to the sources table first (if it doesn't already exist). Do not allow duplicate constants to exist in the database.

Note that the default database user is not authorized to upload content to the database. You need an elevated user.