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A298800
Triangle read by rows: T(n,k) = number of Ringel ladders of order n and genus k.
0
2, 14, 2, 38, 24, 2, 70, 184, 2, 118, 648, 256, 2, 198, 1656, 2240, 2, 342, 3752, 9728, 2560, 2, 614, 8152, 31168, 25600, 2, 1142, 17544, 86784, 132096, 24576, 2, 2182, 37816, 225728, 504320, 278528, 2, 4246, 81768, 566784, 1649152, 1662976, 229376, 2, 8358, 177048, 1393600, 4945920, 7335936, 2916352
OFFSET
1,1
LINKS
Esther Hunt Tesar, Genus distribution of Ringel ladders, Discrete Mathematics 216.1-3 (2000): 235-252.
EXAMPLE
Triangle begins:
2, 14,
2, 38, 24,
2, 70, 184,
2, 118, 648, 256,
2, 198, 1656, 2240,
2, 342, 3752, 9728, 2560,
2, 614, 8152, 31168, 25600,
...
PROG
(PARI) T(n, k) = 2^(3*k+1)*binomial(n-k, k) + 2^(3*k)*binomial(n-k, k-1) + (2^(n+k) - 2^(3*k-3))*binomial(n-k+1, k-2) + (2^(n+k+1) - 2^(3*k-2))*binomial(n-k+1, k-1);
tabf(nn) = {for(n=1, nn, for(k=0, ceil((n+1)/2), print1(T(n, k), ", "); ); print(); ); }; \\ Michel Marcus, May 24 2018
CROSSREFS
Sequence in context: A221234 A133420 A227628 * A138907 A336837 A276189
KEYWORD
nonn,tabf
AUTHOR
N. J. A. Sloane, Feb 02 2018
EXTENSIONS
Corrected and extended by Michel Marcus, May 24 2018
STATUS
approved