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Numbers k for which the GCD of the k-th primorial number and its totient (A058250) sets record.
3

%I #11 Mar 02 2020 09:38:33

%S 1,2,4,5,9,10,15,16,17,23,27,28,35,39,40,41,43,49,56,57,61,62,64,66,

%T 69,72,73,76,77,91,92,96,97,102,103,104,107,111,114,117,119,127,128,

%U 137,139,143,146,150,154,155,166,171,181,182,186,195,196,201,208,214,215

%N Numbers k for which the GCD of the k-th primorial number and its totient (A058250) sets record.

%H Amiram Eldar, <a href="/A071349/b071349.txt">Table of n, a(n) for n = 1..10000</a>

%F If A058250(m) > A058250(k) for all k < m then m is a term.

%t q[n_] := Product[Prime[i], {i, 1, n}]; fq[n_] := Product[Prime[i] - 1, {i, 1, n}];

%t a=0; Do[s=GCD[q[n], fq[n]]; If[s>a, a=s; Print[n]], {n, 1, 1000}]

%Y Cf. A058250, A002110, A000010, A005867, A071350.

%K nonn

%O 1,2

%A _Labos Elemer_, May 21 2002