This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139145 #8 Mar 19 2024 13:01:43 %S A139145 1,1,2,1,2,4,6,1,2,4,6,16,20,36,42,1,2,4,6,16,20,36,42,256,272,400, %T A139145 420,1296,1332,1764,1806,1,2,4,6,16,20,36,42,256,272,400,420,1296, %U A139145 1332,1764,1806,65536,65792,73984,74256,160000,160400,176400,176820,1679616 %N A139145 a(1) = 1, a(2*n) = a(n)^2, a(2*n+1) = a(n)*(a(n)+1). %F A139145 a(2^n - 1) = A007018(n-1). %o A139145 (Python) %o A139145 from functools import lru_cache %o A139145 @lru_cache(maxsize=None) %o A139145 def A139145(n): return (m:=A139145(n>>1))*(m+(n&1)) if n>1 else 1 # _Chai Wah Wu_, Mar 19 2024 %Y A139145 Cf. A007018. %K A139145 nonn %O A139145 1,3 %A A139145 _Reinhard Zumkeller_, Apr 10 2008