Fibonacci Sequence Generator

How to use it

1. Set the F(0) and F(1) starting values. Both accept whole numbers, including negative ones.
2. Choose a term count from 1 to 500. Every term equals the sum of the previous two.
3. The table lists each term with its ratio to the previous term and how far that ratio sits from the golden ratio.
4. Press Export CSV to download the full table, or Copy to put a short report on the clipboard.
5. Everything recomputes as you type; nothing leaves your browser.

Common use cases

• Classroom demos - show the first 20 terms and watch ratios converge toward 1.618.
• Algorithm practice - generate reference sequences to test iterative or memoized implementations.
• Large-number exercises - ask for 500 terms and read a 104-digit result without precision loss.
• Spreadsheet seeding - export CSV and continue analysis in Excel, Sheets or a notebook.

Why it stays private

The sequence is computed in your browser with BigInt arithmetic. There is no server call, no upload, and the CSV is assembled locally before download.

FAQ

Q: Why BigInt instead of regular numbers? A: F(499) has 104 decimal digits, far beyond the 15-16 significant digits a double can hold. BigInt keeps every digit exact, so large sequences stay correct.

Q: What is the ratio column showing? A: F(n) divided by F(n-1), truncated to 40 decimal digits. For the classic 0,1 start it converges toward the golden ratio, about 1.6180339887.

Q: What does the distance column mean? A: It shows the order of magnitude of the gap between the ratio and the golden ratio, written like ~1e-39. Smaller means closer; after 40 shared digits it reads 0.

Q: Can I use custom starting values? A: Yes. Any whole numbers work, including negatives. The recurrence still holds, though the ratio convergence only matches the golden ratio for the standard Fibonacci start.