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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 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.)