OEIS
Shares rank 4 of 18 reference websites by recommenders
Free online database of integer sequences; people use it to look up a sequence from its first few terms and to find background information on it.
Free online database of integer sequences; people use it to look up a sequence from its first few terms and to find background information on it.
10 people gave an opinion
- recommend it
- 9
- criticize it
- 1
- approval share
- 90%
Recommended in 6 of 13 months
- November 2025: not recommended
- December 2025: recommended
- January 2026: not recommended
- February 2026: recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: not recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 9 people recommend itNeeds 10 or more, not met.
- 9 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 6 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Look up sequences from first few terms
“I've solved a lot of otherwise seemingly quite hard problems by numerically/brute-force finding the first few terms then asking OEIS”
Comment from 23 Jun 2026 in “My Mathematical Regression” “"Compute the first few terms and plug into OEIS" is very high on the reward:effort scale”
Comment from 22 Jun 2026 in “My Mathematical Regression” Shows whether a sequence already exists
“Before you pick a number check if that sequence exists and someone might share your interest”
Comment from 30 Apr 2026 in “There were 91 Powerball big prize winners on April 29” “searching that sequence on OEIS should give a lot of good information”
Comment from 7 Jul 2026 in “Ask HN: Where are the good search engines for mathematical formulas?” Useful for maths reading and practice
“the OEIS is an excellent resource for both readinh and sharpening one's amateur teeth”
Comment from 23 Feb 2026 in “Six Math Essentials” “The encyclopedia of integer sequences can be quite useful”
Comment from 7 Jul 2026 in “Ask HN: Where are the good search engines for mathematical formulas?”
Other reference websites people recommend
The four most recommended other reference websites, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Sheldon Brown's Bicycle Technical Info | 49 | 0 | 100% | 6 | 19 yrs4 owners | Approved |
| Animated Knots by Grog | 14 | 1 | 93% | 2 | — | — |
| Ian's Shoelace Site | 10 | 1 | 91% | 4 | — | Approved |
| OEISThis page | 9 | 1 | 90% | 6 | — | — |
| RF Cafe | 9 | 2 | 82% | 1 | — | — |
What people said
7 of the 10 comments that mention it, newest first. Each links to the original comment.
“The encyclopedia of integer sequences can be quite useful”
“searching that sequence on OEIS should give a lot of good information”
“I've solved a lot of otherwise seemingly quite hard problems by numerically/brute-force finding the first few terms then asking OEIS”
“"Compute the first few terms and plug into OEIS" is very high on the reward:effort scale”
“Before you pick a number check if that sequence exists and someone might share your interest”
“A related resource in maths is the OEIS”
“the OEIS is an excellent resource for both readinh and sharpening one's amateur teeth”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.