A160457 a(n) = n^2 - 2*n + 2.

2, 1, 2, 5, 10, 17, 26, 37, 50, 65, 82, 101, 122, 145, 170, 197, 226, 257, 290, 325, 362, 401, 442, 485, 530, 577, 626, 677, 730, 785, 842, 901, 962, 1025, 1090, 1157, 1226, 1297, 1370, 1445, 1522, 1601, 1682, 1765, 1850, 1937, 2026, 2117, 2210, 2305, 2402, 2501, 2602, 2705, 2810

Offset

0,1

Comments

Competition number of the complete bipartite graph K_{n,n}.

Formula given on p. 3 of Sano's article.

Links

Table of n, a(n) for n=0..54.

Yoshio Sano, The competition numbers of regular polyhedra, arXiv:0905.1763 [math.CO], 2009.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

a(n) = a(n-1) + 2*n - 3 (with a(0)=2). - Vincenzo Librandi, Dec 03 2010

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

G.f.: (2 - 5*x + 5*x^2)/(1-x)^3.

a(n) = A002522(n-1). - Michel Marcus, Feb 03 2016

a(n) = (1/4)*(A002378(n) + A002378(n-1) + A002378(n-2) + A002378(n-3)). - Peter Bala, Jun 11 2024

E.g.f.: exp(x)*(2 - x + x^2). - Elmo R. Oliveira, Nov 13 2024

Mathematica

Table[n^2-2*n+2, {n, 0, 5!}] (* Vladimir Joseph Stephan Orlovsky, Dec 29 2010 *)
LinearRecurrence[{3, -3, 1}, {2, 1, 2}, 60] (* Harvey P. Dale, Mar 29 2015 *)

Prog

(PARI) vector(100, n, n--; n^2 - 2*n + 2)

Crossrefs

Cf. A002378, A002522, A160450.

Sequence in context: A117715 A330962 A327194 * A107087 A279955 A280339

Adjacent sequences: A160454 A160455 A160456 * A160458 A160459 A160460

Keyword

easy,nonn

Author

Jonathan Vos Post, May 14 2009

Extensions

More terms from Vincenzo Librandi, Nov 08 2009

Sequence corrected by Joerg Arndt, Dec 03 2010

Status

approved