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 A358452 #6 Nov 21 2022 12:31:19 %S A358452 1,1,1,1,-3,3,-3,5,-8,5,-11,36,-45,41,-72,142,-223,311,-493,851,-1243, %T A358452 1823,-3204,5336,-7906,12083,-20134,33133,-51685,81568,-133556,215363, %U A358452 -340155,547916,-895895,1442323,-2300704,3718260,-6056908,9787064,-15755664,25541623 %N A358452 The inverse Euler transform of p(n) = n if n is prime, otherwise 1. %C A358452 Conjecture: signum(a(n)) + (-1)^n = 0 for n >= 3. %H A358452 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>. %H A358452 Wiki, <a href="https://oeis.org/wiki/Euler_transform">Euler_transform</a> %p A358452 # The function EulerInvTransform is defined in A358451. %p A358452 a := EulerInvTransform(n -> ifelse(isprime(n), n, 1)): %p A358452 seq(a(n), n = 0..41); %p A358452 # Using EULERi the sequence is returned without a(0) and has offset 1. %p A358452 f := n -> ifelse(isprime(n), n, 1): EULERi([seq(f(n), n = 1..41)]); %Y A358452 Cf. A089026, A219224. %K A358452 sign %O A358452 0,5 %A A358452 _Peter Luschny_, Nov 21 2022