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A367050
G.f. satisfies A(x) = 1 + x*A(x)^4 + x^2*A(x)^3.
3
1, 1, 5, 29, 198, 1469, 11518, 93875, 787392, 6752175, 58929541, 521718814, 4674070602, 42296077935, 386027716280, 3549332631052, 32845586854208, 305685481682970, 2859315003009776, 26866125820982711, 253457922829307765, 2399910588283502630
OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..floor(n/2)} binomial(3*n-3*k+1,k) * binomial(4*n-5*k,n-2*k)/(3*n-3*k+1).
PROG
(PARI) a(n) = sum(k=0, n\2, binomial(3*n-3*k+1, k)*binomial(4*n-5*k, n-2*k)/(3*n-3*k+1));
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 03 2023
STATUS
approved