Identify this standard-deck solitaire with a 7x7 tableau
It sounds like a variation of Scorpion. 

Scorpion also uses 7x7 layout, but with a sub rectangle of face-down cards (the exact size varies) rather than a triangular arrangement like you describe.

And it builds King-to-Ace in place (in the tableau) rather than moving Aces up and stacking Ace-to-King above the tableau.