%I #10 Jun 24 2024 08:46:22
%S 1,4,16,71,322,1455,6558,29548,133146,599998,2703794,12184181,
%T 54905857,247423522,1114970351,5024416818,22641646338,102030577247,
%U 459782762029,2071929748572,9336785189996,42074572144477,189601622519548,854406199035948,3850230516227419
%N Number of compositions of 6*n-4 into parts 1 and 6.
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (7,-15,20,-15,6,-1).
%F a(n) = A005708(6*n-4).
%F a(n) = Sum_{k=0..n} binomial(n+1+5*k,n-1-k).
%F a(n) = 7*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).
%F G.f.: x*(1-x)^3/((1-x)^6 - x).
%F a(n) = A373958(n) - A373958(n-1).
%o (PARI) a(n) = sum(k=0, n, binomial(n+1+5*k, n-1-k));
%Y Cf. A099242, A371125, A373302, A373958, A373960.
%Y Cf. A005708.
%K nonn,easy
%O 1,2
%A _Seiichi Manyama_, Jun 23 2024