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 A258290 #11 Apr 13 2025 03:15:22 %S A258290 0,1,5,24,59,456,1448,6868,19749,69364,236356,1526956,3717440, %T A258290 22858340,122553540,474051984,954720543,5726109024,19329586520, %U A258290 92051285020,319059863484,1271796704788,4829219746964,29791326914640,74372011398840,340296661452300 %N A258290 Arithmetic derivative of central binomial coefficients, cf. A000984. %H A258290 Reinhard Zumkeller, <a href="/A258290/b258290.txt">Table of n, a(n) for n = 0..1000</a> %F A258290 a(n) = A003415(A000984(n)). %F A258290 Central terms in triangle A258197: a(n) = A258197(2*n,n). %t A258290 ad[n_] := n * Plus @@ ((Last[#]/First[#]) & /@ FactorInteger[n]); ad[0] = ad[1] = 0; a[n_] := ad[Binomial[2*n, n]]; Array[a, 26, 0] (* _Amiram Eldar_, Apr 13 2025 *) %o A258290 (Haskell) %o A258290 a258290 = a003415 . a000984 %Y A258290 Cf. A000984, A003415, A258197. %K A258290 nonn %O A258290 0,3 %A A258290 _Reinhard Zumkeller_, May 26 2015