

A207540


Degrees (with multiplicity) of simple surface singularities (ADE singularities, Du Val singularities, double rational points, Gorenstein quotient singularities, Klein singularities).


0



2, 4, 6, 6, 6, 8, 8, 10, 10, 10, 12, 12, 12, 14, 14, 14, 16, 16, 18, 18, 18, 18, 20, 20, 22, 22, 22, 24, 24, 26, 26, 26, 28, 28, 30, 30, 30, 30
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OFFSET

1,1


COMMENTS

Adapted from Table 3, p. 46, Dolgachev.


LINKS



FORMULA

With multiplicity: {4k+2, k => 1} and {2k+2, k => 0} and {2n2, n => 4} and {12, 18, 30}.


EXAMPLE

(6, 6, 6) because 4*1 + 2 = 6 (corresponding to isomorphism class A_4), 2*2 + 2 = 6 (corresponding to isomorphism class A_5), 2*4  2 = 6 (corresponding to isomorphism class D_4).
The greatest element in this sequence with multiplicity 4 is 30, corresponding to the sporadic E_8.


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



