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 A166637 #17 Feb 05 2025 07:50:44
%S A166637 1,7,14,49,28,98,42,343,196,196,70,686,84,294,392,2401,112,1372,126,
%T A166637 1372,588,490,154,4802,784,588,2744,2058,196,2744,210,16807,980,784,
%U A166637 1176,9604,252,882,1176,9604,280,4116,294,3430,5488,1078,322,33614,1764
%N A166637 Totally multiplicative sequence with a(p) = 7*(p-1) for prime p.
%H A166637 G. C. Greubel, <a href="/A166637/b166637.txt">Table of n, a(n) for n = 1..10000</a>
%F A166637 Multiplicative with a(p^e) = (7*(p-1))^e. If n = Product p(k)^e(k) then a(n) = Product (7*(p(k)-1))^e(k).
%F A166637 a(n) = A165828(n) * A003958(n) = 7^bigomega(n) * A003958(n) = 7^A001222(n) * A003958(n).
%t A166637 DirichletInverse[f_][1] = 1/f[1]; DirichletInverse[f_][n_] :=
%t A166637 DirichletInverse[f][n] = -1/f[1]*Sum[f[n/d]*DirichletInverse[f][d], {d, Most[Divisors[n]]}]; muphi[n_] := MoebiusMu[n]*EulerPhi[n]; a[m_] := DirichletInverse[muphi][m]; Table[a[m]*7^(PrimeOmega[m]), {m, 1, 100}] (* _G. C. Greubel_, May 20 2016 *)
%t A166637 f[p_, e_] := (7*(p-1))^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Oct 17 2023 *)
%o A166637 (PARI) a(n) = {my(f = factor(n)); for (k=1, #f~, f[k,1] = 7*(f[k,1]-1)); factorback(f);} \\ _Michel Marcus_, May 21 2016
%Y A166637 Cf. A001222, A003958, A165828.
%K A166637 nonn,easy,mult
%O A166637 1,2
%A A166637 _Jaroslav Krizek_, Oct 18 2009