1,2

(1!^1!)!=1 -> 1 digit; (2!^2!)!=24 -> 2 digits; (3!^3!)!=veryverylargenumber -> 197573 digits; (4!^4!)!=?!...

Contribution from Jon E. Schoenfield (jonscho(AT)hiwaay.net), Dec 21 2008: (Start)

(3!^3!)! = (6^6)! = 46656! = 6.8964...*10^197572

(4!^4!)! = (24^24)! = 1333735776850284124449081472843776! = 1.1463...*10^43600856616158353989522412378215476 (End)

a[n_]:=Length[IntegerDigits[(n!^n!)! ]];

Sequence in context: A167518 A006935 A070833 this_sequence A124362 A058435 A151606

Adjacent sequences: A152472 A152473 A152474 this_sequence A152476 A152477 A152478

nonn,base,bref

Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 05 2008

a(4) from Jon E. Schoenfield (jonscho(AT)hiwaay.net), Dec 21 2008