A048164 a(0)=1, a(n+1)=1+(2^(2^n)+1)*a(n).

1, 4, 21, 358, 92007, 6029862760, 25898063359598159721, 477734946799221833229035410333259818858, 162564778457687820218065957445498785826947155451688293007128627114802460256107

Offset: 0

Author

N. J. A. Sloane, E. M. Rains

Keywords

• nonn
• nice
• easy

Comments

a(n) = height of lattice of orthogonal arrays with 2^2^n runs.

Links

• E. M. Rains, N. J. A. Sloane and J. Stufken, The Lattice of N-Run Orthogonal Arrays, J. Stat. Planning Inference, 102 (2002), 477-500 (Abstract, pdf, ps)

Crossrefs

Cf. A039930, A048638.

Programs

Mathematica

RecurrenceTable[{a[0]==1,a[n]==1+(2^(2^(n-1))+1)a[n-1]},a,{n,10}] (* Harvey P. Dale, Dec 13 2013 *)

Formula

a(n) converges to nearest integer to c*(2^(2^n)-1), where c = 1.403936827882178... (see A048649).