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 A109646 Triangle, read by rows, of the number of different isotemporal classes of rotationally distinct diasters with n (rows) total peripheral edges with k (columns) peripheral edges on one side. 0
 1, 1, 1, 3, 1, 6, 1, 8, 6, 1, 10, 12, 1, 12, 15, 10, 1, 14, 18, 20, 1, 16, 21, 24, 15, 1, 18, 24, 28, 30, 1, 20, 27, 32, 35, 21, 1, 22, 30, 36, 40, 42, 1, 24, 33, 40, 45, 48, 28, 1, 26, 36, 44, 50, 54, 56, 1, 28, 39, 48, 55, 60, 63, 36, 1, 30, 42, 52, 60, 66, 70, 72, 1, 32, 45, 56, 65 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS See A092481 for the definition of isotemporal class. A109622 is the sum of rows. REFERENCES B. de Bivort. Isotemporal classes of diasters, beachballs and daisies. Preprint, 2005. LINKS FORMULA for k=0, a(n, k)=1 for k>0 and n!=k, a(n, k)=(n-k)k+(n-k)+k+1 for k>0 and n=k, a(n, k)=(1/2)(k^2+3k+2) EXAMPLE Row 0 has 1 element, a diaster with no peripheral edges - a singleton edge - for which there is only a single isotemporal class. Row 1 has 1 element, the diaster with a single peripheral edge - two edges sharing a single vertex - for which there is a single isotemporal class. Row 2 has 2 elements, corresponding to the diaster with a two peripheral edges on a single side and the diaster with a single peripheral edge on either side, with 1 and 3 isotemporal classes respectively. CROSSREFS Cf. A092481, A109622. Sequence in context: A300244 A168111 A309491 * A199783 A318772 A317496 Adjacent sequences:  A109643 A109644 A109645 * A109647 A109648 A109649 KEYWORD easy,nonn,tabf AUTHOR Benjamin de Bivort (bivort(AT)fas.harvard.edu), Aug 04 2005 STATUS approved

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Last modified September 19 04:52 EDT 2019. Contains 327187 sequences. (Running on oeis4.)