|
| |
|
|
A349676
|
|
Iterated Pillai's arithmetical function: a(1) = 2, for n >= 2, a(n) = A018804(a(n-1)).
|
|
0
|
|
|
|
2, 3, 5, 9, 21, 65, 225, 1365, 14625, 223125, 5630625, 376228125, 38759765625, 3471767578125, 934835712890625, 497199051298828125, 613613372156103515625, 2538878964828409423828125, 25280374785655551910400390625, 243473923053903449878692626953125, 9202204429788304689688510894775390625
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
|
|
|
FORMULA
|
a(1) = 2, a(n) = A018804(a(n-1)) for n >= 2.
|
|
|
EXAMPLE
|
a(5) = f(f(f(f(a(1))))) = 21. Here f represents A018804.
|
|
|
MATHEMATICA
|
f[p_, e_] := (e*(p - 1)/p + 1) * p^e; pil[n_] := Times @@ f @@@ FactorInteger[n]; NestList[pil, 2, 20] (* Amiram Eldar, Nov 24 2021 *)
|
|
|
PROG
|
(PARI) f(n) = sumdiv(n, d, n*eulerphi(d)/d); \\ A018804
lista(nn) = my(a = 2); for (n=1, nn, print1(a, ", "); a = f(a); ); \\ Michel Marcus, Nov 24 2021
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
|
|
|
EXTENSIONS
|
|
|
|
STATUS
|
approved
|
| |
|
|
