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));
A370187
Coefficient of x^n in the expansion of ( (1+x)^2 * (1+x+x^3)^2 )^n.
Original entry on oeis.org
1, 4, 28, 226, 1940, 17214, 155914, 1432106, 13289076, 124276528, 1169346298, 11057293526, 104986087178, 1000248093420, 9557756114130, 91559051752596, 879027678226452, 8455595252761536, 81476137225450096, 786286875175380088, 7598503022428758570
Offset: 0
-
a(n, s=3, t=2, u=2) = 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.