A178497 5 followed by A145503.

5, 3, 13, 193, 37633, 1416317953, 2005956546822746113, 4023861667741036022825635656102100993, 16191462721115671781777559070120513664958590125499158514329308740975788033

Offset: 0

Author

Roger L. Bagula, May 28 2010

Keywords

• nonn

Comments

The first 6 entries of the sequence are primes.

The Fermat numbers F(.)=A000215(.) obey equations with flipped signs of the +-2 if compared with the a(n) (see the formula section): F(n) = Prod{i=0,...,n-1} F(i)+2 and F(n) = F(n-1) *(F(n-1)-2)+2. - Vladimir Shevelev, Dec 08 2010

Crossrefs

Cf. A000215, A110407, A178428, A178427.

Programs

Mathematica

Clear[a, n];
a[ -1] := 1; a[0] := 5;
a[n_] := a[n] = Product[a[i], {i, 0, n - 1}] - 2;
Table[a[n], {n, 0, 10}]

Formula

a(n)= ( product_{i=0..n-1} a(i)) -2, n>=1.

a(n) = a(n-1)*( a(n-1)+2 )-2, n>=2. - Vladimir Shevelev, Dec 08 2010

Extensions

Definition simplified by the Assoc. Eds. of the OEIS, Jun 07 2010