A288706 Number of (undirected) paths in the n-sun graph.

108, 614, 3840, 26937, 211722, 1852300, 17900118, 189670655, 2188938928, 27349969842, 368010246500, 5307501200421, 81699366763710, 1337244268935960, 23195236251394954, 425069874742963563, 8207267847726907028, 166543057722717660670, 3543666872978746093608, 78898851731990085876113

Offset

3,1

Links

Andrew Howroyd, Table of n, a(n) for n = 3..200

Andrew Howroyd, Derivation of formula, Jun 2025.

Eric Weisstein's World of Mathematics, Graph Path.

Eric Weisstein's World of Mathematics, Sun Graph.

Prog

(PARI) a(n) = {my(s=sum(k=1, n, sum(i=0, min(k, n-k), binomial(k, i)*binomial(n-1, k+i-1)*2^i*(k-1)!*((5*k-2*i) - n*i/(k+i) + if(k>1, (i*(i+3) + 4*k*(k-1-i))/(k-1)))/k))); (2*(n-1) - 1 + s)*n/2} \\ Andrew Howroyd, Jun 17 2025

Crossrefs

Cf. A234627.

Sequence in context: A233685 A160919 A129027 * A204276 A202194 A386433

Adjacent sequences: A288703 A288704 A288705 * A288707 A288708 A288709

Keyword

nonn

Author

Eric W. Weisstein, Jun 13 2017

Extensions

a(10) from Eric W. Weisstein, Sep 09 2017

a(11)-a(12) from Eric W. Weisstein, Mar 14 2019

a(13) onwards from Andrew Howroyd, Jun 17 2025

Status

approved