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A274047
Diameter of Generalized Petersen Graph G(n, 2).
1
2, 4, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23, 24, 24, 24, 24, 25
OFFSET
5,1
FORMULA
a(n) = floor((floor(n/2)+5)/2) for n>7.
G.f.: x^5*(2 + 2*x - x^2 + x^3 - 2*x^4 - x^5 + x^6 - x^7)/((1 + x)*(1 - x)^2*(1 + x^2)). - Bruno Berselli, Jun 08 2016
a(n) = 2 + floor(n/4 + 1/2) = A002265(n+10) for n>7. - Bruno Berselli, Jun 08 2016
MATHEMATICA
a[n_] := GraphDiameter[PetersenGraph[n, 2]]; Table[a[n], {n, 5, 30}]
LinearRecurrence[{1, 0, 0, 1, -1}, {2, 4, 3, 4, 4, 5, 5, 5}, 100] (* Harvey P. Dale, Jan 12 2020 *)
PROG
(PARI) a(n)=if(n>7, (n\2+5)\2, [4, 3, 2][n%3+1]) \\ Charles R Greathouse IV, Jun 08 2016
(Magma) [n le 7 select [4, 3, 2][n mod 3+1] else 2+Floor(n/4+1/2): n in [5..90]]; // Bruno Berselli, Jun 08 2016 - after Charles R Greathouse IV
CROSSREFS
Cf. A002265.
Sequence in context: A073127 A339099 A098604 * A226644 A083172 A287797
KEYWORD
nonn,easy
AUTHOR
Nick Mayers, Jun 07 2016
STATUS
approved