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A118623
a(0) = 1, a(n+1) = a(n)^2 + number of divisors of a(n).
0
1, 2, 6, 40, 1608, 2585680, 6685741062420, 44699133553728910336256592, 1998012540454093724746522398047564450017935663454544
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OFFSET
0,2
LINKS
Table of n, a(n) for n=0..8.
Index entries for sequences of form a(n+1)=a(n)^2 + ...
FORMULA
a(n) =
A000290
(a(n-1)) +
A000005
(a(n-1)).
MATHEMATICA
NestList[#^2+DivisorSigma[0, #]&, 1, 10] (*
Harvey P. Dale
, Nov 18 2022 *)
CROSSREFS
Cf.
A007018
.
Sequence in context:
A337699
A370615
A051185
*
A000612
A319633
A367365
Adjacent sequences:
A118620
A118621
A118622
*
A118624
A118625
A118626
KEYWORD
nonn
,
changed
AUTHOR
Reinhard Zumkeller
, May 09 2006
STATUS
approved
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Last modified September 17 05:28 EDT 2024. Contains 375985 sequences. (Running on oeis4.)