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 A280692 #17 Jun 16 2025 16:26:22
%S A280692 0,0,0,0,0,0,0,6,0,-6,0,12,0,-6,0,36,0,24,0,6,0,-24,0,66,0,-24,60,18,
%T A280692 0,18,0,150,-20,-42,0,120,0,-42,-10,72,0,42,0,-12,60,-48,0,264,0,0,
%U A280692 -30,0,0,216,0,132,-30,-78,0,138,0,-72,120,540,0,0,0,-30,-30,24,0,462,0,-96,60,-18,0,24,0,330,420,-114,0,246
%N A280692 a(n) = A003961(n) - A250469(n).
%H A280692 Antti Karttunen, <a href="/A280692/b280692.txt">Table of n, a(n) for n = 1..10067</a>
%F A280692 a(n) = A003961(n) - A250469(n).
%t A280692 f[n_] := f[n] = Which[n == 1, 1, PrimeQ@ n, NextPrime@ n, True, Times @@ Replace[FactorInteger[n], {p_, e_} :> f[p]^e, 1]]; g[n_] := If[n == 1, 0, PrimePi@ FactorInteger[n][[1, 1]]]; Function[s, MapIndexed[ Function[{m, n}, f@ n - Lookup[s, g[n] + 1][[m]] + Boole[n == 1]][#1, First@ #2] &, #] &@ Map[Position[Lookup[s, g@ #], #][[1, 1]] &, Range@ 120]]@ PositionIndex@ Array[g, 10^4] (* _Michael De Vlieger_, Mar 09 2017, Version 10 *)
%o A280692 (Scheme) (define (A280692 n) (- (A003961 n) (A250469 n)))
%Y A280692 Cf. A003961, A250469, A249820, A280492, A280497, A280498, A280702.
%Y A280692 Cf. A280693 (gives the positions of zeros).
%Y A280692 Cf. also arrays A083221 and A246278.
%K A280692 sign
%O A280692 1,8
%A A280692 _Antti Karttunen_, Mar 08 2017