(33s) OEIS A2516: EARLIEST SEQUENCE WITH A(A(N)) = 2N

[Gerald H]

Takes a real integer from the stack & returns A2516(N) to stack.

https://oeis.org/A002516

Maximum number of recursions is 7, ie any number with a power of 2 greater than 2^7 as a factor will produce the
“XEQ OVERFLOW”
error.

Earliest sequence with
A(A(N)) = 2N.

Code:

1.    LBL C
2.    STO N
3.    CLx
4.    RMDR(N:2)
5.    x=0?
6.    GTO D
7.    CLx
8.    RMDR(N:4)-1
9.    x≠0?
10.    GTO E
11.    CLx
12.    N+2
13.    RTN
1.    LBL E
2.    CLx
3.    (N-2)*2
4.    RTN
1.    LBL D
2.    CLx
3.    N/2
4.    XEQ C
5.    STO N
6.    RCL+N
7.    RTN

C: LN = 62
E: LN = 19
D: LN = 24