A260262 Number of digits of hyperfactorial(hyperfactorial(n)).

1, 1, 5, 10703, 1614696745, 28812381422477890, 100652205682053466439353073, 100862590668529143951825397261798321446, 39596172587764149886638486692811308322476202830248047, 7942534398808419809836601901425429825855063583537701822391757140131840

Offset: 0

Author

Matthew Campbell, Jul 21 2015

Keywords

• nonn
• easy
• base

Examples

			Hyperfactorial(Hyperfactorial(1)) = 1.  There is 1 digit in the number 1.  Because of this, a(1) = 1.
		

Links

• Matthew Campbell, Table of n, a(n) for n = 0..27

Crossrefs

Cf. A002109, A055642.

Programs

Mathematica

Table[Floor[Log[10, Hyperfactorial[Hyperfactorial[n]]]] + 1, {n, 0, 3}]

PARI

hyperfactorial(n)=prod(k=2,n,k^k)
first(m)=vector(m,i,#digits(hyperfactorial(hyperfactorial(i)))) \\ Anders Hellström, Aug 29 2015

Formula

a(n) = floor(log_10(hyperfactorial(hyperfactorial(n))))+1.

a(n) = A055642(A002109(A002109(n))).