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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

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

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Last modified February 26 09:33 EST 2020. Contains 332277 sequences. (Running on oeis4.)