IsNotSeq      ← ¬/↧=1⧈-
Subsets       ← /◇⊂≡(□≡□⧅<)↘1
Nonseqsubsets ← ▽⊸≡◇IsNotSeq Subsets ⟜¤↘1⇡
≡(&p$"Subseqs of sequence of 1-_:\n_"-1⟜Nonseqsubsets) [4 5 6]