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 A341512 #23 Mar 23 2021 16:16:48 %S A341512 0,1,2,11,2,36,4,85,46,58,2,324,4,120,120,575,2,693,4,566,248,172,6, %T A341512 2340,94,270,788,1176,2,1800,6,3661,348,358,336,5967,4,492,548,4210,2, %U A341512 3744,4,1820,2490,744,6,15372,380,2271,720,2826,6,11304,392,8760,992,946,2,15480,6,1232,5164,22631,636,5904,4,3866 %N A341512 a(n) = A341529(n) - A341528(n) = (sigma(n)*A003961(n)) - (n*sigma(A003961(n))). %H A341512 Antti Karttunen, <a href="/A341512/b341512.txt">Table of n, a(n) for n = 1..8191</a> %H A341512 Antti Karttunen, <a href="/A341512/a341512.txt">Data supplement: n, a(n) computed for n = 1..65537</a> %H A341512 <a href="/index/Pri#gaps">Index entries for primes, gaps between</a> %H A341512 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a> %H A341512 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %F A341512 a(n) = A341529(n) - A341528(n) = (sigma(n)*A003961(n)) - (n*sigma(A003961(n))). %F A341512 For all primes p, a(p) = (q*(p+1)) - (p*(q+1)) = (pq + q) - (pq + p) = q - p = A001223(A000720(p)), where q = nextprime(p) = A003961(p). %F A341512 And in general, a(p^e) = (q^e * (p^(e+1)-1)/(p-1)) - ((p^e) * (q^(e+1)-1)/(q-1)), where q = A003961(p). %F A341512 Thus, a(p^2) = (p + 1)*q^2 - p^2*q - p^2, %F A341512 a(p^3) = (p^2 + p + 1)*q^3 - p^3*q^2 - p^3*q - p^3, %F A341512 a(p^4) = (p^3 + p^2 + p + 1)*q^4 - p^4*q^3 - p^4*q^2 - p^4*q - p^4, %F A341512 etc. %t A341512 Array[#2 DivisorSigma[1, #1] - #1 DivisorSigma[1, #2] & @@ {#, Times @@ Map[#1^#2 & @@ # &, FactorInteger[#] /. {p_, e_} /; e > 0 :> {Prime[PrimePi@ p + 1], e}] - Boole[# == 1]} &, 68] (* _Michael De Vlieger_, Feb 22 2021 *) %o A341512 (PARI) %o A341512 A003961(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); }; \\ From A003961 %o A341512 A341528(n) = (n*sigma(A003961(n))); %o A341512 A341529(n) = (sigma(n)*A003961(n)); %o A341512 A341512(n) = (A341529(n)-A341528(n)); %Y A341512 Cf. A000203, A000720, A001223, A003961, A003973, A286385, A341528, A341529, A341530. %Y A341512 Cf. Sequences A001359, A029710, A031924 give the positions of 2's, 4's and 6's in this sequence, or at least subsets of such positions. %K A341512 nonn,look %O A341512 1,3 %A A341512 _Antti Karttunen_, Feb 22 2021