Navigate the explorer using up/down arrows
Press space to expand once
Press enter to expand recursively
Backspace to unexpand

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BMS
Y-sequence
HPrSS
LPrSS
Grandparent Sequence System

Ordinal explorer

Navigate the explorer using the up/down arrow keys
Press space to expand the selected term once
Press enter to expand recursively
Press backspace to un-expand
Left/right arrow keys also expand and unexpand