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 A378978 #15 Dec 13 2024 15:22:15 %S A378978 1,1,0,1,2,-4,4,1,-3,-2,8,-12,10,0,-12,1,14,-19,16,-10,-12,4,20,-28,7, %T A378978 6,-12,-8,26,-48,28,1,-12,10,-4,-51,34,12,-12,-26,38,-56,40,-4,-54,16, %U A378978 44,-60,25,-17,-12,-2,50,-64,4,-24,-12,22,56,-120,58,24,-60,1,8,-72,64,2,-12,-56,68,-115,70,30,-72,4,20 %N A378978 Deficiency of even numbers: a(n) = 4*n - sigma(2*n). %H A378978 Antti Karttunen, <a href="/A378978/b378978.txt">Table of n, a(n) for n = 1..32769</a> %H A378978 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>. %F A378978 a(n) = A033879(2*n) = 4*n - A062731(n). %t A378978 a[n_]:= 4*n - DivisorSigma[1,2*n]; Array[a,77] (* _Stefano Spezia_, Dec 13 2024 *) %o A378978 (PARI) %o A378978 A033879(n) = (n+n-sigma(n)); %o A378978 A378978(n) = A033879(2*n); %Y A378978 Even bisection of A033879. %Y A378978 Topmost row of A378979. %Y A378978 Cf. A000203, A033879, A062731. %Y A378978 Cf. also A344587, A377879. %K A378978 sign %O A378978 1,5 %A A378978 _Antti Karttunen_, Dec 13 2024