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%I #4 Feb 13 2021 14:49:55
%S 10,23,26,31,44,57,60,65,68,78,81,86,99,112,115,120,133,146,149,154,
%T 157,167,170,175,178,188,201,204,209,212,222,225,230,243,256,259,264,
%U 277,290,293,298,301,311,314,319,332,345,348,353,366,379,382,387,390
%N Numbers that occur twice in the Wythoff ceiling array (A341260).
%C No term occurs more than twice. Conjecture: the difference sequence, (13,3,5,13,13,3,5,...) has only 4 distinct terms: 3,5,10,13.
%e 10 is in rows 1 and 4; 23 is in rows 2 and 9; 26 is in rows 1 and 10.
%t W[n_, k_] := Fibonacci[k + 1] Ceiling[n*GoldenRatio] + (n - 1) Fibonacci[k];
%t t = Table[W[n - k + 1, k], {n, 500}, {k, n, 1, -1}] // Flatten; (* A341260 *)
%t s = Sort[t]; ss = s[[Select[Range[Length[s]] - 1, s[[#]] == s[[# + 1]] &]]] (* A341261 *)
%Y Cf. A341260.
%K nonn
%O 1,1
%A _Clark Kimberling_, Feb 09 2021
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