(33s) OEIS A4444: Nimsum N+3

[Gerald H]

Takes a natural number from the stack & returns A4444(N) to stack.

https://oeis.org/A004444

Nth in natural order for run of four integers in natural order reversed, then next four integers in natural order reversed ….
Preserves stack.

Code:

1.    LBL B
2.    STO N
3.    CLx
4.    N+(-1)^N+2*(-1)^IDIV(N:2)
5.    RTN

B: LN = 40        CK = 25E5