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%I #7 Feb 20 2024 10:44:39
%S 2,6,20,42,110,156,272,342,506,812,870,930,1332,1640,1722,1806,2162,
%T 2756,3422,3660,4290,4422,4830,4970,5256,6006,6162,6806,7832,9312,
%U 10100,10302,10506,10920,11342,11772,11990,12656,12882,16002,16770,17030,18632,18906,19182
%N Oblong numbers of the form (k-1)*k where k is the product of an odd number of distinct primes.
%H Amiram Eldar, <a href="/A370494/b370494.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A002378(A030059(n)-1).
%F Sum_{n>=1} 1/a(n) = (A368250 + A033150 - 1)/2 = 0.776922504035... .
%t Table[n*(n - 1), {n, Select[Range[150], MoebiusMu[#] == -1 &]}]
%o (PARI) lista(kmax) = forsquarefree(k=1, kmax, if(moebius(k) == -1, print1(k[1]*(k[1]-1), ", ")));
%Y Complement of A370495 within A368249.
%Y Cf. A002378, A030059, A033150, A368250.
%K nonn,easy
%O 1,1
%A _Amiram Eldar_, Feb 20 2024
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