Excel BI - Excel Challenge 693

excel-challenges
excel-formulas
🔰 Generate a sequence taking first 4 numbers as 1, 2, 3, 4.
Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 693

Challenge Description

🔰 Generate a sequence taking first 4 numbers as 1, 2, 3, 4. In this sequence, take the block of last 4 numbers and next 2 numbers would sum of first and third term and sum of second and fourth terms. Derive 100 terms of this series.

Solutions

library(tidyverse)
library(readxl)

path = "Excel/693 Generate a sequence.xlsx"
test  = read_excel(path, range = "A1:A101")

start = list(1, 2, 3, 4)
for (i in 1:50) {
  start = append(start, c(sum(start[[length(start) - 3]], start[[length(start) - 1]]),
                          sum(start[[length(start) - 2]], start[[length(start)]])))
}
df = data.frame(a = unlist(start[1:100]))
all.equal(df$a, test$`Answer Expected`)
# TRUE
  • Logic: Read the workbook ranges needed for the challenge; Iterate through the sequence until the rule is satisfied.
  • Strengths: The algorithm is explicit about the sequence rule, so the control flow is easy to validate against the prompt.
  • 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 non-obvious part is the local rule inside the loop, because that rule determines the whole output.
import pandas as pd

path = "693 Generate a sequence.xlsx"
test = pd.read_excel(path, usecols="A", nrows=101)

start = [1, 2, 3, 4]
while len(start) < 101:
    start += [start[-4] + start[-2], start[-3] + start[-1]]
start = start[:100]
df = pd.DataFrame({'Sequence': start})

print(df["Sequence"].equals(test["Answer Expected"])) # 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.