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 A380951 #5 Mar 07 2025 06:40:40 %S A380951 0,1,11,41,515,1467,7847,20081,397923,961255,4552845,10609519, %T A380951 97582823,221879063,999384495,2232200321,79200753059,174525593247, %U A380951 764867505329,1667683433315,14479516479981,31302413221189,134846186300129,289480028851479,4956344862563975,10577819852813291 %N A380951 a(n) = 2^(2*n - HammingWeight(n)) * [x^n] ((1 - x)^(-5/2) - (x - 1)^(-2)). %p A380951 gf := (1 - x)^(-5/2) - (x - 1)^(-2): ser := series(gf, x, 32): %p A380951 seq(2^(2*n - add(convert(n, base, 2))) * coeff(ser, x, n), n = 0..22); %Y A380951 Cf. A046161, A000120, A098597, A001790, A173384, A380952. %K A380951 nonn %O A380951 0,3 %A A380951 _Peter Luschny_, Mar 06 2025