OFFSET
1,1
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..10000
Benedek Nagy and H. Mujahed, Detour index for body-centred cubic grid with unit cells connected in a row, Comptes Rendus de l'Académie Bulgare des Sciences, 74(11), 1581-1589 (2021).
Eric Weisstein's World of Mathematics, Detour Index
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = (25*n^3 + 180*n^2 - 13*n)/3.
From Stefano Spezia, May 28 2024: (Start)
G.f.: 2*x*(32 + 21*x - 28*x^2)/(1 - x)^4.
E.g.f.: exp(x)*x*(192 + 255*x + 25*x^2)/3. (End)
MATHEMATICA
LinearRecurrence[{4, -6, 4, -1}, {64, 298, 752, 1476}, 50] (* Paolo Xausa, May 28 2024 *)
PROG
(PARI) a(n) = (25*n^3 + 180*n^2 - 13*n)/3 \\ Andrew Howroyd, Oct 24 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Benedek Nagy, Oct 24 2023
STATUS
approved