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Number sequence calculator

Compare constant differences and constant ratios, then extend each matching arithmetic or geometric model.

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Number sequence calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Spaces separate values; 1,000 is one value.

Answer

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Compare constant differences and constant ratios, then extend each matching arithmetic or geometric model.

More results
Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Saved scenario
Save the current answer, then change an input to compare. This clears when you leave.
Formula and assumptions
A finite sequence never determines a unique continuation. This tool checks only arithmetic and geometric models; a match is a possible pattern, not proof of the intended rule. It does not infer arbitrary polynomial, recursive or puzzle rules.
In a list, use spaces, new lines, semicolons, or commas followed by a space. A comma between groups of three digits is a thousands separator.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
Scratch calculator
Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.
Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.
Links include your inputs and settings. Anyone with the link can see them, so leave out private text. Files and generated results are left out; random draws run again.
Keyboard shortcuts
Updated 
Using Number sequence calculator
Compare constant differences and constant ratios, then extend each matching arithmetic or geometric model.
A finite sequence never determines a unique continuation. This tool checks only arithmetic and geometric models; a match is a possible pattern, not proof of the intended rule. It does not infer arbitrary polynomial, recursive or puzzle rules.
Next: Fibonacci sequence calculator
Next: Statistics calculator
A worked example
For sequence terms separated by spaces = 3 7 11 15, additional terms = 3, matching model = Arithmetic.
Before you use the result
A finite sequence never determines a unique continuation. This tool checks only arithmetic and geometric models; a match is a possible pattern, not proof of the intended rule. It does not infer arbitrary polynomial, recursive or puzzle rules.
Cite this page
ToolOctopus. “Number sequence calculator.” Updated 2026-09-29. https://tooloctopus.com/number-sequence-calculator.
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