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User:Hugh Darwen

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Software developer for IBM, 1967-2004. Specialised in relational databases (see Now retired but part-time lecturer at Warwick University, England.

I have no formal qualifications in mathematics but I have a keen amateur interest, especially insofar as it applies to my own special subject in computer science.

In about 1970 I had been looking for numbers, like 1, 36, and 1225, that have the property of being both square and triangular: "triangular squares". Noting that 36 is 2^2*3^2 and 1225 is 5^2*7^2, a sequence started to emerge that had a strange similarity to Fibonacci. On reading about this web site in "Alex's Adventures in Numberland" by Alex Bellos, I decided to see what it had to say about "my" sequence and of course I quickly found A002965. In A002965, (a(2n)*a(2n-1))^2 is triangular. I believe the sequence generates all the natural numbers that have this property. As far as I can see, this facet is not mentioned in the page for A002965.