# On-Line Encyclopedia of Integer Sequences outage reports and status

Canonical page: https://iszdown.com/now/seis

Status: Website reachable in latest check

24-hour window (UTC): 2026-10-18T04:00:00.000Z to 2026-10-19T04:00:00.000Z

Recorded outage reports in this window: 0

Last successful estimated-activity check: No usable observation available

The On-Line Encyclopedia of Integer Sequences is an online database of integer sequences. It was created and maintained by Neil Sloane while researching at AT&T Labs. He transferred the intellectual property and hosting of the OEIS to the OEIS Foundation in 2009. Sloane is chairman of the OEIS Foundation. OEIS records information on integer sequences of interest to both professional and amateur mathematicians, and is widely cited. As of March 2021 it contains 341,962 sequences, making it the largest database of its kind. Each entry contains the leading terms of the sequence, keywords, mathematical motivations, literature links, and more, including the option to generate a graph or play a musical representation of the sequence. The database is searchable by keyword, by subsequence, or by any of 16 fields.

## How to interpret this page

Estimated down reports are based on US Google Trends problem-intent searches. Values are relative activity from 0 to 100, not counts of submitted reports. The HTML chart averages samples into ten-minute intervals. Partial samples are excluded and missing samples are not invented.

Recorded outage reports and estimated activity are separate signals. Neither confirms that every user is affected. Missing or stale data does not establish that a service is working.

Methodology: https://iszdown.com/methodology

## Citation

Cite [On-Line Encyclopedia of Integer Sequences on Iszdown](https://iszdown.com/now/seis), include your access time and the observation time above, and qualify estimated activity as an estimate. Recheck before describing current status. Iszdown is independent of the monitored provider.

## Estimated activity samples

No usable Google Trends samples are available for this service in this window.

## Evidence and recovery

Website reachable in latest check. The public website responded; signed-in features and APIs were not tested.

No recent recovery can be established from available evidence.

## Website measurements

Successful sampled checks (24h): 100% (1/1). Restricted checks: 0. Median response: 127 ms. P95 response: 127 ms.

These are sampled public website checks from one US server, not continuous uptime or authenticated app/API tests. Missing data stays unknown.


## Related services

- [On-Line Encyclopedia of Integer Sequences](https://iszdown.com/now/seis)