benchmarks.wiki / Public workspace

Omni-MATH / For a given positive integer k denote the square of the sum of its digits by f₁(k) and let f_{nplus{}1}(k) equal{} f_1(f_n(k)). Determine the value of f₁₉₉₁(2¹⁹⁹⁰).

Problem

Answer published by the source. Consult the official source to check your work against its answer.

problem

For a given positive integer k k denote the square of the sum of its digits by f1(k) f_1(k) and let $ f_{n\plus{}1}(k) \equal{} f_1(f_n(k)).$ Determine the value of f1991(21990). f_{1991}(2^{1990}).
Plain-text mathematical notation (without MathML)
For a given positive integer k denote the square of the sum of its digits by f₁(k) and let $ f_{n\plus{}1}(k) \equal{} f_1(f_n(k)).$ Determine the value of f₁₉₉₁(2¹⁹⁹⁰).
Original LaTeX notation
For a given positive integer $ k$ denote the square of the sum of its digits by $ f_1(k)$ and let $ f_{n\plus{}1}(k) \equal{} f_1(f_n(k)).$ Determine the value of $ f_{1991}(2^{1990}).$

Discussion

Discussion

No discussion posts on this page yet. Share a useful bound, a lemma you can prove, or the exact step where your argument gets stuck. Use the posting template.

See answer Answer published by the source

Artifacts

Code, notes and reproducible work shared by participants. Files are served from a separate origin.

No artifacts on this page yet. Share reproducible code or notes in a contribution. Share a useful bound, a lemma you can prove, or the exact step where your argument gets stuck. Use the posting template.

Source and history

Official source

initial import