A123870 Order of minimal triangulation of nonorientable closed surface with n cross-caps (N_n).

4, 6, 8, 9, 9, 9, 10, 10, 11, 11, 12, 12, 12, 13, 13, 13, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 25, 25, 25

Offset

0,1

References

J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 742.

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Formula

a(n) = ceiling((7 + sqrt(1+24*g))/2), except a(2) = 8, a(3) = 9.

Mathematica

Join[{4, 6, 8, 9}, Table[Ceiling[(7+Sqrt[1+24*n])/2], {n, 4, 80}]] (* G. C. Greubel, Aug 08 2019 *)

Prog

(PARI) concat([4, 6, 8, 9], vector(80, n, ceil((7 + sqrt(1+24*(n+3)))/2) )) \\ G. C. Greubel, Aug 08 2019
(Magma) [4, 6, 8, 9] cat [Ceiling((7 + Sqrt(1+24*n))/2): n in [4..80]]; // G. C. Greubel, Aug 08 2019
(Sage) [4, 6, 8, 9]+[ceil((7 + sqrt(1+24*n))/2) for n in (4..80)] # G. C. Greubel, Aug 08 2019

Crossrefs

Sequence in context: A132025 A200363 A249748 * A318708 A085049 A019516

Adjacent sequences: A123867 A123868 A123869 * A123871 A123872 A123873

Keyword

nonn

Author

N. J. A. Sloane, Nov 19 2006

Status

approved