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URL: https://oeis.org/A275587

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A275587
a(1) = 0; thereafter a(n) = s^s where s = Sum_{k=1..n-1} a(k).
1
0, 1, 1, 4, 46656
OFFSET
1,4
COMMENTS
a(2) = 1 by the convention that 0^0 = 1. a(6) = 46662^46662 = 1471657830...9021753344, which has 217864 decimal digits.
MATHEMATICA
a[0] = 0; a[1] = 1; a[n_] := a[n] = #^# &@ Sum[a[k], {k, 1, n - 1}]; Table[a[n], {n, 0, 5}] (* Michael De Vlieger, Aug 04 2016 *)
PROG
(PARI) a(n) = local(s); if(n==1, 0, if(n>1, s = sum(k=1, n - 1, a(k)); s^s))
CROSSREFS
Sequence in context: A053937 A259160 A173138 * A132638 A046882 A165812
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Aug 02 2016
STATUS
approved