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 A326129 #20 Jul 29 2020 16:37:56 %S A326129 1,1,2,1,4,0,6,1,1,2,10,1,12,4,6,1,16,1,18,1,10,8,22,6,1,10,2,21,28, %T A326129 12,30,1,18,14,22,1,36,16,22,10,40,12,42,1,4,20,46,1,1,1,30,3,52,12, %U A326129 38,2,34,26,58,3,60,28,2,1,46,12,66,1,42,4,70,1,72,34,2,3,58,12,78,1,1,38,82,7,62,40,54,2,88,2,70,1,58,44,70,30 %N A326129 a(n) = gcd(A326127(n), A326128(n)). %C A326129 Question: Are there any other numbers than those in A000396 that satisfy a(k) = A326128(k)? %C A326129 See also comments in A336641, where all such k should reside. - _Antti Karttunen_, Jul 29 2020 %H A326129 Antti Karttunen, <a href="/A326129/b326129.txt">Table of n, a(n) for n = 1..20000</a> %F A326129 a(n) = n - A336645(n). - _Antti Karttunen_, Jul 29 2020 %o A326129 (PARI) %o A326129 A326127(n) = (sigma(n)-core(n)-n); %o A326129 A326128(n) = (n-core(n)); %o A326129 A326129(n) = gcd(A326127(n), A326128(n)); %Y A326129 Cf. A000396, A007913, A326126, A326127, A326128. %Y A326129 Cf. also A009194, A325385, A325813, A325975, A326046, A326047, A326048, A326056, A326057, A326060, A326062, A326130, A326140, A326144, A336641, A336645. %K A326129 nonn %O A326129 1,3 %A A326129 _Antti Karttunen_, Jun 09 2019