|
|
A101303
|
|
a(n) = sigma() [A000203] applied n times to prime(n).
|
|
1
|
|
|
3, 7, 28, 60, 360, 1512, 3276, 16256, 65528, 261120, 79360, 1098240, 13852800, 25261824, 79536128, 1040179456, 1710858240, 13815410400, 71687577600, 137707384824, 151060010112, 1932916285440, 4212741841200, 508764077015040, 24560669041920, 26379664917984
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(1)= 3 = sigma(2);
a(2)= 7 = sigma(sigma(3));
a(3)= 28 = sigma(sigma(sigma(5)));
a(4)= 60 = sigma(sigma(sigma(sigma(7)))).
|
|
MAPLE
|
a:= n-> (numtheory[sigma]@@n)(ithprime(n)):
|
|
MATHEMATICA
|
f[n_] := DivisorSigma[1, n]; Table[ Nest[f, Prime[n], n], {n, 25}] (* Robert G. Wilson v, Dec 22 2004 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|