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a(n) is the least positive integer > a(n-1) and not a(i)*a(j)-a(k) for 1 <= i <= j <= k <= n, where a(1) = 1.
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%I #20 Apr 21 2021 04:39:47

%S 1,3,4,7,10,13,16,19,22,25,28,31,34,37,40,43,46,49,52,55,58,61,64,67,

%T 70,73,76,79,82,85,88,91,94,97,100,103,106,109,112,115,118,121,124,

%U 127,130,133,136,139,142,145,148,151,154,157,160,163,166,169,172

%N a(n) is the least positive integer > a(n-1) and not a(i)*a(j)-a(k) for 1 <= i <= j <= k <= n, where a(1) = 1.

%C Conjecture: This is the increasing sequence of numbers congruent to 1 mod 3, with 3 inserted.

%C Conjecture holds for n <= 1300. - _Sean A. Irvine_, Oct 12 2019

%Y Cf. A026477.

%K nonn

%O 1,2

%A _Clark Kimberling_

%E Corrected and extended by _Clark Kimberling_, Oct 12 2019