A271393 a(1) = 3, a(n+1) = (3^a(n)-1)/2.

3, 13, 797161

Offset: 1

Author

Thomas Ordowski, Apr 06 2016

Keywords

• nonn

Comments

The next term is too large to include.

The terms a(1), a(2), and a(3) are primes.

The next term a(4) is a composite number, a pseudoprime to base 3.

If a(n) is a pseudoprime to base 3, then a(n+1) is a pseudoprime to base 3.

Note that a(n) divides a(n+1)-1 for every n.

a(4) has 380343 digits. - Altug Alkan, Apr 09 2016

References

• R. Steuerwald (1948), see A005935.

Crossrefs

Cf. A005935 (see Steuerwald's theorem), A007013, A028491.

Programs

Mathematica

NestList[(3^# - 1)/2 &, 3, 3] (* Michael De Vlieger, Apr 06 2016 *)