Golfing Chain (Cops' Thread) This is a Cops and Robbers challenge. For the Robbers' thread, go here.

The Cops have three tasks.
1) Pick a sequence from the OEIS.  

2) Pick a language (this is suggested to be a golflang, but doesn't have to be) that, when given input n, outputs A(n) (where A(n) is the sequence chosen) using all usual code-golf rules.
Call this language LA and code CA.
For example, Jelly and Jelly_code.  

3) Then, pick a different language (this is suggested to be a non-golflang, but doesn't have to be) and write code that takes no input and outputs code CA, again following all usual code-golf rules. (Note: this can be obfuscated code and doesn't necessarily need to be golfed, but the longer this code is the easier it will be for the robbers to crack your submission.)
Call this language LB and code CB.
For example, Python and Python_code.

The Cop's submission to this challenge is the sequence (specified whether 0- or 1-indexed), the name of the two languages LA and LB (and which one solves which part), and the byte-count of CB only. Keep the actual code of both parts, and the length of CA, secret.

For the Cop, links to documentation for LA and LB, or an interpreter (or a TIO link, since that includes both), are appreciated but not required.

The Robber's challenge is to select a Cops' entry and write code CC in the same LB language that outputs some code in the same LA language that solves the original OEIS task. The length of CC can be no longer than the length of CB as revealed by the cop (though may be shorter). Note: The code produced by CC does not have to match CA.

For our example, this means that the Robber has to write Python code that outputs Jelly code that solves the original OEIS sequence, and that Python code has to be no longer than the length revealed by the Cop.

Winning conditions

Answers that have not been cracked in a week can have their solutions revealed, at which point they are considered Safe. Note that if you don't reveal your solution after a week, it can still be cracked. The Cop with the shortest Safe answer wins.
OEIS A000041, cracked by ETHproductions
Let's try it the other way around: golflang generates non-golflang.

a(n) = number of partitions of n (the partition numbers).


a(n) (0-indexed) is returned by a JavaScript function (ES6)
The program that outputs the JS function is written in Jelly
The length of the Jelly program is 35 bytes

Intended solution

    Jelly: “¦ṚoIwƭ- ḊFæSḂ¥¶Ẉ|ḊJƓƝʋnrB⁾’b28+40Ọ


    which outputs


    JS: C=(A,B=A)=&gt;A&lt;0?0:A?B?C(A,B-1)+C(A-B,B):0:1