Excel BI - Excel Challenge 831

excel-challenges

excel-formulas

🔰 Find first 1000 terms of this sequence.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 831

Challenge Description

🔰 Find first 1000 terms of this sequence.

Solutions

library(tidyverse)
library(readxl)

path = "Excel/800-899/831/831 Recaman Sequence.xlsx"
test = read_excel(path, range = "A1:A1001") %>% pull()

recaman_sequence <- function(n){
  reduce(2:n, 
         .init = list(seq = 0L, seen = 0L),
         .f = function(state, k){
           seq <- state$seq
           seen <- state$seen
           prev <- last(seq)
           cand <- prev - (k - 1L)
           next_val <- if(cand > 0L && !(cand %in% seen)) cand else prev + (k - 1L)
           list(seq = c(seq, next_val), seen = c(seen, next_val))
         })$seq
}

result = recaman_sequence(1000)
all.equal(result, test)

Logic: Read the workbook ranges needed for the challenge.
Strengths: The code maps the workbook rule into a compact, reproducible pipeline.
Areas for Improvement: The solution assumes the workbook layout and selected ranges remain stable, so any structural change in the sheet would require small adjustments.
Gem: The elegant part is how little code is needed once the correct intermediate representation is chosen.

import pandas as pd

path = "800-899/831/831 Recaman Sequence.xlsx"
test = pd.read_excel(path, usecols="A", nrows=1001).iloc[:, 0].tolist()

def recaman(n):
    a=[0]; s={0}
    for k in range(1,n):
        x=a[-1]-k
        a.append(x if x>0 and x not in s else a[-1]+k); s.add(a[-1])
    return a

print(recaman(1000) == test) # True

The Python version keeps the algorithm explicit, which helps when the challenge depends on a greedy or iterative rule.

Difficulty Level

Easy / Medium

The business rule is clear, though the workbook still needs a few transformation steps to reach the expected output.