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THE FEUTEX TOOLKIT

Fibonacci Index Values

Calculate Fibonacci and Lucas numbers at a bounded nonnegative integer index.

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01 Your input
02 Your result
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FormulaFibonacci = round((((1+sqrt(5))/2)**n-((1-sqrt(5))/2)**n)/sqrt(5)); Lucas = round(((1+sqrt(5))/2)**n+((1-sqrt(5))/2)**n)
Sources and model references

How to use this tool

  1. Enter the labeled inputs using consistent units.
  2. Check the stated assumptions and calculate.
  3. Review each output and compare another input scenario.

Try this example

{
  "n": 10
}

Accuracy and scope

Closed-form floating-point evaluation; limited to index 70 for reliable integer-sized outputs. Finite floating-point arithmetic; results can lose precision near singular or extreme inputs.

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