OFFSET
3,1
LINKS
Colin Barker, Table of n, a(n) for n = 3..1000
Eric Weisstein's World of Mathematics, Dipyramidal Graph
Eric Weisstein's World of Mathematics, Hamiltonian Path
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = 2*n*(31 - 20*n + 4*n^2) for n > 3.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n > 7.
G.f.: 2*x^3*(18 - 12*x + 23*x^2 - 2*x^3 - 3*x^4) / (1 - x)^4. - Colin Barker, May 09 2019
MATHEMATICA
Join[{36}, Table[2 n (31 - 20 n + 4 n^2), {n, 4, 20}]]
Join[{36}, LinearRecurrence[{4, -6, 4, -1}, {120, 310, 660, 1218}, 20]]
CoefficientList[Series[-2 (-18 + 12 x - 23 x^2 + 2 x^3 + 3 x^4)/(-1 + x)^4, {x, 0, 20}], x]
PROG
(PARI) Vec(2*x^3*(18 - 12*x + 23*x^2 - 2*x^3 - 3*x^4) / (1 - x)^4 + O(x^40)) \\ Colin Barker, May 09 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, May 06 2019
STATUS
approved