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1,1

Table of n, a(n) for n=1..80.

a(n) = A000005(A073065(n)-1).

A133992 := proc(n) p := ithprime(n) ; p*ithprime(p)-1 ; numtheory[tau](%) ; end proc: seq(A133992(n), n=1..80) ; # R. J. Mathar, Jun 28 2010

Table[DivisorSigma[0, Prime[n]*Prime[Prime[n]] - 1], {n, 100}] (* Wesley Ivan Hurt, Feb 03 2017 *)

Cf. A000005, A073065.

Sequence in context: A060968 A151569 A016635 * A294094 A290288 A126215

Adjacent sequences: A133989 A133990 A133991 * A133993 A133994 A133995

nonn,easy

Giovanni Teofilatto, Jan 09 2008

Definition clarified by D. S. McNeil, Jun 28 2010

approved