A370185
Coefficient of x^n in the expansion of (1+x+x^3)^(2*n).
Original entry on oeis.org
1, 2, 6, 26, 126, 612, 2970, 14534, 71838, 357884, 1793296, 9026976, 45612450, 231224060, 1175422590, 5989693176, 30586693182, 156483812892, 801908994852, 4115509738188, 21149522157816, 108817959549416, 560500440662872, 2889915938877078, 14913928051929426
Offset: 0
-
a(n, s=3, t=2, u=0) = sum(k=0, n\s, binomial(t*n, k)*binomial((t+u)*n-k, n-s*k));
A370186
Coefficient of x^n in the expansion of ( (1+x) * (1+x+x^3)^2 )^n.
Original entry on oeis.org
1, 3, 15, 90, 583, 3913, 26790, 185839, 1301575, 9183681, 65181645, 464858661, 3328503814, 23913207750, 172295708971, 1244484142765, 9008351053031, 65332552755149, 474622993450725, 3453219378684621, 25158758123093013, 183521479226172667, 1340195580366321837
Offset: 0
-
a(n, s=3, t=2, u=1) = sum(k=0, n\s, binomial(t*n, k)*binomial((t+u)*n-k, n-s*k));
A372371
Coefficient of x^n in the expansion of ( (1+x+x^3)^2 / (1+x) )^n.
Original entry on oeis.org
1, 1, 1, 7, 25, 61, 187, 666, 2137, 6676, 22001, 73217, 239923, 789517, 2624182, 8729527, 29026553, 96790606, 323546416, 1082566763, 3626148425, 12163438539, 40847087821, 137294721676, 461890741843, 1555264438186, 5240857508017, 17672768973979, 59634361740734
Offset: 0
-
a(n, s=3, t=2, u=-1) = sum(k=0, n\s, binomial(t*n, k)*binomial((t+u)*n-k, n-s*k));
Showing 1-3 of 3 results.