Here is the link to the Wikipedia article on this topic.
keywords:
[Recreational Mathematics]
[sequence of integers]
[sequences of integers]

a quote from the author of the article:
“There are two partially contradicting trends in high school mathematics education. On one hand, we want mathematical knowledge to be based on a solid logical base (rigor). On the other hand, we want this knowledge to be rich both in content and applications.”
— Petar S. Kenderov
Here’s the link.
keywords:
[mathematics]
[content]
[applications]
[rigor]
[mathematics education]
[mathematical modeling]
[mathematical modelling]
[inquiry education]
[computational thinking]
[quantitative models]
[dynamic mathematics software (DMS)]
[dynamic mathematical software (DMS)]