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a(n) = least positive integer > a(n-1) and not of the form a(i) + a(j) + a(k) for 1 <= i < j < k <= n.
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%I #19 Aug 06 2018 12:24:00

%S 1,2,3,4,5,13,14,15,25,26,27,37,38,48,49,50,60,61,71,72,73,83,84,94,

%T 95,96,106,107,117,118,119,129,130,140,141,142,152,153,163,164,165,

%U 175,176,186,187,188,198,199,209,210,211,221,222,232,233,234,244,245,255

%N a(n) = least positive integer > a(n-1) and not of the form a(i) + a(j) + a(k) for 1 <= i < j < k <= n.

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,1,-1).

%F {1, 5, 13} union {n congruent 2, 3, 4, 14, 15 mod 23}, proved by Matthew Akeran. - _Ralf Stephan_, Nov 15 2004

%F G.f.: (9*x^11-7*x^10+9*x^8+7*x^5+x^4+x^3+x^2+x+1)*x/(x^6-x^5-x+1). - _Alois P. Heinz_, Aug 06 2018

%Y Cf. A003278, A033627, A075122, A075123.

%K nonn,easy

%O 1,2

%A _Clark Kimberling_

%E Edited by _Floor van Lamoen_, Sep 02 2002