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%I #6 Dec 06 2024 11:29:44
%S 1,2,6,3,15,15,105,210,70,70,770,2310,30030,30030,30030,15015,255255,
%T 255255,4849845,4849845,4849845,4849845,111546435,37182145,7436429,
%U 7436429,22309287,22309287,646969323,3234846615,100280245065,200560490130,200560490130,200560490130
%N a(n) = denominator(Sum_{k=1..n} 1/P(k)), where P(k) = A006530(k) is the greatest prime dividing k for k >= 2, and P(1) = 1.
%C See A378678 for more details.
%H Amiram Eldar, <a href="/A378679/b378679.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) | A034386(n).
%t Denominator@ Accumulate[Table[1/FactorInteger[n][[-1, 1]], {n, 1, 34}]]
%o (PARI) lista(nmax) = {my(s = 1); print1(1, ", "); for(n = 2, nmax, f = factor(n); s += 1/f[#f~, 1]; print1(denominator(s), ", "));}
%Y Cf. A006530, A034386, A057155, A378678 (numerators).
%K nonn,easy,frac,new
%O 1,2
%A _Amiram Eldar_, Dec 03 2024