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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..52. 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 Adjacent sequences: A298797 A298798 A298799 * A298801 A298802 A298803 KEYWORD nonn,tabf AUTHOR N. J. A. Sloane, Feb 02 2018 EXTENSIONS Corrected and extended by Michel Marcus, May 24 2018 STATUS approved

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Last modified December 1 18:36 EST 2023. Contains 367500 sequences. (Running on oeis4.)