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%I #20 Sep 25 2022 11:10:42
%S 0,0,0,0,0,0,1,1,2,2,3,4,5,6,7,8,9,10,11,13,14,16,17,19,21,23,25,27,
%T 29,31,33,35,38,40,43,45,48,51,54,57,60,63,66,69,72,76,79,83,86,90,94,
%U 98,102,106,110,114,118,122,127,131,136,140,145
%N a(n) = floor( n(n-1)/26 ).
%H G. C. Greubel, <a href="/A011879/b011879.txt">Table of n, a(n) for n = 0..300</a>
%H <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1).
%F G.f.: (x^6 (1+x (-1+x (1+(-1+x) x))))/(1+x (-2+x (1+x^11 (-1+(2-x) x)))). - _Peter J. C. Moses_, Jun 01 2014
%F a(n)= +2*a(n-1) -a(n-2) +a(n-13) -2*a(n-14) +a(n-15). - _R. J. Mathar_, Aug 11 2021
%t Table[Floor[n(n-1)/26], {n,0,600}] (* _G. C. Greubel_, Sep 03 2015 *)
%t Join[{0},Floor[#/13]&/@Accumulate[Range[0,70]]] (* _Harvey P. Dale_, Apr 26 2020 *)
%o (PARI) a(n) = n*(n-1)\26; \\ _G. C. Greubel_, Sep 03 2015
%K nonn,easy
%O 0,9
%A _N. J. A. Sloane_.
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