cp's OEIS Frontend

A257934 Expansion of 1/(1-x-x^2-x^3-x^4+x^5+x^6+x^7).

%I A257934 #22 Mar 21 2017 11:06:45
%S A257934 1,1,2,4,8,14,26,48,89,163,300,552,1016,1868,3436,6320,11625,21381,
%T A257934 39326,72332,133040,244698,450070,827808,1522577,2800455,5150840,
%U A257934 9473872,17425168,32049880,58948920,108423968,199422769,366795657,674642394,1240860820,2282298872,4197802086,7720961778
%N A257934 Expansion of 1/(1-x-x^2-x^3-x^4+x^5+x^6+x^7).
%C A257934 This sequence counts partially ordered partitions of (n) into parts (1,2,3,4) in which the position (order) of the 4's are unimportant. For example the permutations of (43421) are counted as permutations of (321)=6.
%H A257934 <a href="/index/Par#partN">Index entries for related partition-counting sequences</a>
%H A257934 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1,1,-1,-1,-1).
%F A257934 a(n)= a(n-1) + a(n-2) + a(n-3) + a(n-4) - a(n-5) - a(n-6) - a(n-7).
%F A257934 G.f.: 1 / ((x-1)*(x+1)*(x^2+1)*(x^3+x^2+x-1)). - _Colin Barker_, May 17 2015
%e A257934 a(6)=26; these are (42=24),(411=141=114),(33),(321=six),(3111=four),(222),(2211=six),(21111=five),(111111).
%o A257934 (PARI) Vec(1 / ((x-1)*(x+1)*(x^2+1)*(x^3+x^2+x-1)) + O(x^100)) \\ _Colin Barker_, May 17 2015
%Y A257934 Cf. A258000, A257863.
%K A257934 nonn,easy
%O A257934 0,3
%A A257934 _David Neil McGrath_, May 13 2015
%E A257934 Missing term (6320) inserted by _Colin Barker_, May 17 2015