A000643 -id:A000643 - cp's OEIS frontend

A000659 a(n) = 2^a(n-1) + a(n-2).

0, 0, 1, 2, 5, 34, 17179869189

Offset: 0

nonn

The next term has 5171655948 digits. - Franklin T. Adams-Watters, Jul 03 2009

Join[{a=0,b=0},Table[c=2^b+a;a=b;b=c,{n,5}]] (* Vladimir Joseph Stephan Orlovsky, Apr 13 2011 *)
nxt[{a_,b_}]:={b,2^b+a}; NestList[nxt,{0,0},6][[All,1]] (* Harvey P. Dale, Apr 09 2022 *)

A114641 a(n) = 2^(a(n-2) + log_{2}(a(n-1))), a(1)=1, a(2)=2.

Original entry on oeis.org

1, 2, 4, 16, 256, 16777216, 1942668892225729070919461906823518906642406839052139521251812409738904285205208498176

Offset: 1

Yasutoshi Kohmoto, Feb 18 2006

nonn

The subsequent terms are too large to include.

Apparently a(n) = A000643(n+2) - A000643(n+1). - R. J. Mathar, Apr 22 2007

Cf. A112237, A112866.

RecurrenceTable[{a[1]==1,a[2]==2,a[n]==2^(a[n-2]+Log[2,a[n-1]])},a,{n,6}] (* Harvey P. Dale, Aug 23 2013 *)

a(n) = a(n-1) * 2^a(n-2) for n >= 3. - Alois P. Heinz, Jun 28 2021

Definition adapted to offset by Georg Fischer, Jun 18 2021

cp's OEIS Frontend

A000659 a(n) = 2^a(n-1) + a(n-2).

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