cp's OEIS Frontend

a(n) = [x^n] (1+x)^(6*n+1)/(1-x).

a(n) = [x^n] 1/((1-x)^(5*n+1) * (1-2*x)).

a(n) = Sum_{k=0..n} 2^k * (-1)^(n-k) * binomial(6*n+1,k) * binomial(6*n-k,n-k).

a(n) = Sum_{k=0..n} 2^k * binomial(6*n-k,n-k).

G.f.: 1/(1 - 4*x*g^4*(3-g)) where g = 1+x*g^6 is the g.f. of A002295.

G.f.: g^2/((2-g) * (6-5*g)) where g = 1+x*g^6 is the g.f. of A002295.

G.f.: B(x)^2/(1 + 2*(B(x)-1)/3), where B(x) is the g.f. of A004355.

a(n) ~ 2^(6*n-1) * 3^(6*n + 3/2) / (sqrt(Pi*n) * 5^(5*n + 1/2)). - Vaclav Kotesovec, Aug 19 2025

D-finite with recurrence +5*n*(5*n-3) *(25275337086729240289198339046875*n +471647298106881091699147254457046) *(5*n-1)*(5*n-4)*(5*n-2)*a(n) +(78985428396028875903744809521484375*n^6 -559942234844855804767211877804090453801*n^5 +3587636672285250929619857349305543417315*n^4 -10153151347942687598200945831585305558855*n^3 +14794114656715293872778407292185015920550*n^2 -10846691360081598422810600143797325763664*n +3179147242764665659301361496311050364480)*a(n-1) +40*(916451705547792050816664342989042382392*n^6 -15754440652132350078674083937326518806004*n^5 +117614110896134855700514819789186651267682*n^4 -471111363407608954402735569277858473721059*n^3 +1053743992048348087929158710510276422876431*n^2 -1242809524683997363700671579060256757555078*n +603414490131980309336751304501155726403152) *a(n-2) +3072*(-950768355029313182341332806167821761828*n^6 +17097100921628721474237101055297828968024*n^5 -128090998271831890487248970509140383514230*n^4 +509544263618626898681417576914870842148685*n^3 -1132270964907780344616429736070172799129247*n^2 +1330655887974191637410201798934319046990726*n -645481184978535641217111809931780144149880) *a(n-3) +884736*(3*n-11) *(6*n-17) *(61801507754400081418308631750717123*n -123657551673181017806623428016627104) *(6*n-19)*(3*n-10)*(2*n-7)*a(n-4)=0. - R. J. Mathar, Aug 26 2025

a(n) = [x^n] (1+x)^(5*n+1)/(1+3*x).

a(n) = [x^n] 1/((1-x)^(4*n+1) * (1+2*x)).

a(n) = Sum_{k=0..n} (-2)^k * 3^(n-k) * binomial(5*n+1,k) * binomial(5*n-k,n-k).

a(n) = Sum_{k=0..n} (-2)^k * binomial(5*n-k,n-k).

G.f.: 1/(1 - x*g^3*(-10+13*g)) where g = 1+x*g^5 is the g.f. of A002294.

G.f.: g^2/((-2+3*g) * (5-4*g)) where g = 1+x*g^5 is the g.f. of A002294.

G.f.: B(x)^2/(1 + 7*(B(x)-1)/5), where B(x) is the g.f. of A001449.

D-finite with recurrence 648*n*(135551509682187347695*n -244103380745409504343) *(4*n-1)*(2*n-1)*(4*n-3)*a(n) +(-33979500619583537984836075*n^5 +130803893690808003041848009*n^4 -168380151442376797602371231*n^3 +62069291513227826684567999*n^2 +49760069127090078338544954*n -39530305857276050670355320)*a(n-1) +40*(-108999332467309598098777*n^5 -28981701912184019189355*n^4 -1554974299825191814369159*n^3 +13581461461293413639358363*n^2 -28599284433109723900055776*n +18909354537435947334628944)*a(n-2) +211200*(5*n-11) *(5*n-9)*(28440609019752807*n +93502568692163852)*(5*n-13)*(5*n-12)*a(n-3)=0. - R. J. Mathar, Aug 26 2025