A303920 G.f.: A(x,y) = (1-y) * Sum_{n>=0} y^n * (1 + x*(1-y)^2)^(n^2).
1, 0, 1, 1, 0, 0, 6, 6, 0, 0, 0, 4, 56, 56, 4, 0, 0, 0, 1, 117, 722, 722, 117, 1, 0, 0, 0, 0, 126, 2982, 12012, 12012, 2982, 126, 0, 0, 0, 0, 0, 84, 6916, 79548, 246092, 246092, 79548, 6916, 84, 0, 0, 0, 0, 0, 36, 10900, 312880, 2322000, 6002824, 6002824, 2322000, 312880, 10900, 36, 0, 0, 0, 0, 0, 9, 12717, 864009, 13617765, 74916306, 170048394, 170048394, 74916306, 13617765, 864009, 12717, 9, 0, 0, 0, 0, 0, 1, 11421, 1825786, 57282026, 604000555, 2669115383, 5489377628, 5489377628, 2669115383, 604000555, 57282026, 1825786, 11421, 1, 0, 0
Offset: 0
Examples
G.f.: A(x,y) = (1-y) * ( 1 + y*(1 + x*(1-y)^2) + y^2*(1 + x*(1-y)^2)^4 + y^3*(1 + x*(1-y)^2)^9 + y^4*(1 + x*(1-y)^2)^16 + y^5*(1 + x*(1-y)^2)^25 + ... ). Explicitly, A(x,y) = 1 + x*(y + y^2) + x^2*(6*y^2 + 6*y^3) + x^3*(4*y^2 + 56*y^3 + 56*y^4 + 4*y^5) + x^4*(y^2 + 117*y^3 + 722*y^4 + 722*y^5 + 117*y^6 + y^7) + x^5*(126*y^3 + 2982*y^4 + 12012*y^5 + 12012*y^6 + 2982*y^7 + 126*y^8) + x^6*(84*y^3 + 6916*y^4 + 79548*y^5 + 246092*y^6 + 246092*y^7 + 79548*y^8 + 6916*y^9 + 84*y^10) + x^7*(36*y^3 + 10900*y^4 + 312880*y^5 + 2322000*y^6 + 6002824*y^7 + 6002824*y^8 + 2322000*y^9 + 312880*y^10 + 10900*y^11 + 36*y^12) + x^8*(9*y^3 + 12717*y^4 + 864009*y^5 + 13617765*y^6 + 74916306*y^7 + 170048394*y^8 + 170048394*y^9 + 74916306*y^10 + 13617765*y^11 + 864009*y^12 + 12717*y^13 + 9*y^14) + x^9*(y^3 + 11421*y^4 + 1825786*y^5 + 57282026*y^6 + 604000555*y^7 + 2669115383*y^8 + 5489377628*y^9 + 5489377628*y^10 + 2669115383*y^11 + 604000555*y^12 + 57282026*y^13 + 1825786*y^14 + 11421*y^15 + y^16) + ... This triangle begins: [1]; [0, 1, 1]; [0, 0, 6, 6, 0]; [0, 0, 4, 56, 56, 4, 0]; [0, 0, 1, 117, 722, 722, 117, 1, 0]; [0, 0, 0, 126, 2982, 12012, 12012, 2982, 126, 0, 0]; [0, 0, 0, 84, 6916, 79548, 246092, 246092, 79548, 6916, 84, 0, 0]; [0, 0, 0, 36, 10900, 312880, 2322000, 6002824, 6002824, 2322000, 312880, 10900, 36, 0, 0]; [0, 0, 0, 9, 12717, 864009, 13617765, 74916306, 170048394, 170048394, 74916306, 13617765, 864009, 12717, 9, 0, 0]; [0, 0, 0, 1, 11421, 1825786, 57282026, 604000555, 2669115383, 5489377628, 5489377628, 2669115383, 604000555, 57282026, 1825786, 11421, 1, 0, 0]; ...
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Crossrefs
Programs
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PARI
/* G.f. by Definition: */ {T(n,k) = my(A = (1-y) * sum(m=0,2*n, y^m * (1 + x*(1-y)^2 +x*O(x^(2*n)) )^(m^2))); polcoeff(polcoeff(A, n,x),k,y)} for(n=0, 10, for(k=0,2*n, print1(T(n,k), ", ")); print("")) -
PARI
/* Continued fraction expression: */ {T(n,k) = my(CF=1, q = 1 + x*(1-y)^2 +x*O(x^(2*n))); for(k=0, n, CF = 1/(1 - q^(4*n-4*k+1)*y/(1 - q^(2*n-2*k+1)*(q^(2*n-2*k+2) - 1)*y*CF)) ); polcoeff(polcoeff((1-y)*CF, n,x),k,y)} for(n=0, 10, for(k=0,2*n, print1(T(n,k), ", ")); print("")) -
PARI
/* G.f. by q-series identity: */ {T(n,k) = my(A =1, q = 1 + x*(1-y)^2 +x*O(x^(2*n))); A = (1-y) * sum(m=0,2*n, y^m*q^m * prod(k=1,m, (1 - y*q^(4*k-3)) / (1 - y*q^(4*k-1) +x*O(x^(2*n))) )); polcoeff(polcoeff(A, n,x),k,y)} for(n=0, 10, for(k=0,2*n, print1(T(n,k), ", ")); print(""))
Formula
GENERATING FUNCTIONS.
(1) A(x,y) = (1-y) * Sum_{n>=0} y^n * (1 + x*(1-y)^2)^(n^2).
(2) A(x,y) = (1-y) * Sum_{n>=0} y^n * q^n * Product_{k=1..n} (1 - q^(4*k-3)*y) / (1 - q^(4*k-1)*y), where q = 1 + x*(1-y)^2, due to a q-series identity.
(3) A(x,y) = (1-y)/(1 - q*y/(1 - q*(q^2-1)*y/(1 - q^5*y/(1 - q^3*(q^4-1)*y/(1 - q^9*y/(1- q^5*(q^6-1)*y/(1 - q^13*y/(1 - q^7*(q^8-1)*y/(1 - ...))))))))), where q = 1 + x*(1-y)^2, a continued fraction due to an identity of a partial elliptic theta function.
FORMULAS INVOLVING TERMS.
Sum_{k=0..2*n} T(n,k) = (2*n)!/n!, for n>=0 (row sums = A001813).
Sum_{k=0..2*n} T(n,k) * (-1)^k = 0, for n>=1 (symmetric rows).
Sum_{k=0..2*n} T(n,k) * 2^k = A265936(n), for n>=1.
Sum_{k=0..2*n} T(n,k) / 2^k = A173217(n) / 4^n, for n>=0.
Sum_{j=0..k^2} T(j,k) = A303922(k), for k>=0 (column sums).
T(n,n) = A303921(n), for n>=0 (diagonal).
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