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a(n) is the least integer k such that 1/(Sum_{j=1..n} 1/phi(k*j)) is an integer.
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%I #18 Feb 21 2021 07:12:11

%S 1,3,4,7,22,31,24,101,53,22,563,149,75,321,310,653,3110,907,5926,

%T 16829,2505,12735,96179,12969,5931,18033,20231,61483,579559,1323199,

%U 1477613,1133209,65051,151643,152567,610799,459949,154553,17006,156863,285170

%N a(n) is the least integer k such that 1/(Sum_{j=1..n} 1/phi(k*j)) is an integer.

%H Seiichi Manyama, <a href="/A341810/b341810.txt">Table of n, a(n) for n = 1..55</a>

%o (PARI) a(n) = my(k=1); while (denominator(1/sum(j=1, n, 1/eulerphi(k*j))) != 1, k++); k; \\ _Michel Marcus_, Feb 20 2021

%Y Inspired by A341799.

%Y Cf. A000010, A341811, A341813.

%K nonn

%O 1,2

%A _Seiichi Manyama_, Feb 20 2021