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Actually, 17 bytes (non-competing)

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes

Actually, 17 bytes

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes

Actually, 17 bytes (non-competing)

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

This submission is non-competing because the ♀ command was added after this challenge.

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes

Actually, 17 bytes (non-competing)

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes

##Actually, 17 bytes (non-competing)

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

This submission is non-competing because the ♀ command was added after this challenge.

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes

Actually, 17 bytes (non-competing)

;a¡;lrR(♀ⁿ@♂≈♀*;░

Try it online!

This submission is non-competing because the ♀ command was added after this challenge.

Explanation:

;a¡;lrR(♀ⁿ@♂≈♀*;░
                   initial stack: [b n] (b = base, n = number)
;                  dupe b
 a                 invert stack
  ¡                n as a base-b integer
   ;lrR            dupe, length, range, reverse
       (♀ⁿ         raise b to each power in range
          @♂≈      create list of integers from base-b string
             ♀*    pairwise multiplication
               ;░  filter out zeroes