A006485 a(n) = (2^(2^n + 1) + 1)/3.

3, 11, 171, 43691, 2863311531, 12297829382473034411, 226854911280625642308916404954512140971, 77194726158210796949047323339125271902179989777093709359638389338608753093291

Offset: 1

Author

Dennis S. Kluk (mathemagician(AT)ameritech.net)

Keywords

• nonn

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Delbert L. Johnson, Table of n, a(n) for n = 1..11
• D. S. Kluk and N. J. A. Sloane, Correspondence, 1979.

Crossrefs

Cf. A001045, A070969.

Programs

Mathematica

lst={};Do[AppendTo[lst, (2^(2^n+1)+1)/3], {n, 9}];lst (* Vladimir Joseph Stephan Orlovsky, Sep 19 2008 *)
Table[(1+2^(2^n+1))/3,{n,10}] (* Harvey P. Dale, Apr 03 2023 *)

PARI

{a(n) = if(n > 0, (2^(2^n + 1) + 1)/3, 0)}; /* Michael Somos, Mar 30 2020 */

Formula

a(n) = A001045(2^n+1) = (3*a(n-1)^2 + 1)/2 - a(n-1). - Michael Somos, Mar 30 2020

a(n) = A070969(n)/3. - Alois P. Heinz, Mar 28 2023