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%I #4 Oct 29 2023 23:04:53
%S 1,4,80,616,6576,41088,1224720,4027392,82260072,4938271560,
%T 635485074048,41135376570624,12236327748685824,411522630337040436,
%U 65843620853926470080,6172839452588538935840,805372326785629836739584,40727551345036946357114880
%N a(n) is the Euler totient function of the concatenation of 1,2,3,...,n.
%F a(n) = phi(A007908(n)) = A000010(A007908(n)).
%Y Cf. A007908, A000010.
%K nonn,base
%O 1,2
%A _Sean A. Irvine_, Oct 29 2023
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