A101303 a(n) = sigma() [A000203] applied n times to prime(n).

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

Offset

1,1

Links

Table of n, a(n) for n=1..26.

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)):
seq(a(n), n=1..30);  # Alois P. Heinz, Oct 03 2018

Mathematica

f[n_] := DivisorSigma[1, n]; Table[ Nest[f, Prime[n], n], {n, 25}] (* Robert G. Wilson v, Dec 22 2004 *)

Crossrefs

Cf. A000203, A090896.

Sequence in context: A232806 A270349 A281701 * A148751 A148752 A148753

Adjacent sequences: A101300 A101301 A101302 * A101304 A101305 A101306

Keyword

nonn,easy

Author

Jorge Coveiro, Dec 22 2004

Extensions

Edited and extended by Robert G. Wilson v, Dec 22 2004

Status

approved