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A057870 Number of singular points on n-th order Chmutov surface. 1
0, 1, 3, 14, 28, 57, 93, 154, 216, 321, 425, 576, 732, 949, 1155, 1450, 1728, 2097, 2457, 2926, 3360, 3941, 4477, 5160, 5808, 6625, 7371, 8334, 9212, 10305, 11325, 12586, 13728, 15169, 16473, 18072, 19548, 21349, 22971, 24986, 26800, 29001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..42.

Eric Weisstein's World of Mathematics, Chmutov Surface. [Gives a formula]

FORMULA

Appears to satisfy a 13-term linear recurrence. - Ralf Stephan, Mar 07 2004

Conjectures from Colin Barker, Jan 02 2020: (Start)

G.f.: x^2*(1 + 3*x + 12*x^2 + 21*x^3 + 27*x^4 + 28*x^5 + 31*x^6 + 25*x^7 + 18*x^8 + 11*x^9 + 3*x^10) / ((1 - x)^4*(1 + x)^3*(1 - x + x^2)*(1 + x + x^2)^2).

a(n) = 2*a(n-2) + a(n-3) - a(n-4) - 2*a(n-5) + a(n-6) + a(n-7) - 2*a(n-8) - a(n-9) + a(n-10) + 2*a(n-11) - a(n-13) for n>13.

(End)

CROSSREFS

Sequence in context: A032041 A031002 A085762 * A256053 A031049 A014696

Adjacent sequences:  A057867 A057868 A057869 * A057871 A057872 A057873

KEYWORD

nonn

AUTHOR

Eric W. Weisstein

STATUS

approved

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Last modified August 7 17:38 EDT 2020. Contains 336278 sequences. (Running on oeis4.)