A006485 a(n) = (2^(2^n + 1) + 1)/3. (Formerly M2912)

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

Offset

1,1

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.

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

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 *)

Prog

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

Crossrefs

Cf. A001045, A070969.

Sequence in context: A132561 A306002 A140538 * A003115 A053888 A118479

Adjacent sequences: A006482 A006483 A006484 * A006486 A006487 A006488

Keyword

nonn

Author

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

Status

approved