A033541 - OEIS

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A033541

Number of irreducible exceptional curves of first kind on del Pezzo surface of degree 9-n.

0, 1, 3, 6, 10, 16, 27, 56, 240 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	COMMENTS	`The case n=1 is exceptional and a(1) could be 0 or 1.`
	REFERENCES	`Yu. I. Manin, Rational surfaces and Galois cohomology, pp. 495-509 of Proc. International Congress Mathematicians, Moscow 1966.` `M. Nagata, On rational surfaces, I, II, Mem. Coll. Sci. Univ. Kyoto, Ser. A., XXXII (No. 3, 1960) and XXXIII (No. 2, 1960).`
	CROSSREFS	`Sequence in context: A054886 A130578 A107068 * A038505 A119971 A094272` `Adjacent sequences: A033538 A033539 A033540 * A033542 A033543 A033544`
	KEYWORD	`fini,full,nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), Feb 13 2002`

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Last modified February 15 17:46 EST 2012. Contains 205835 sequences.