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A120271 Numerator of Sum[ 1/(Prime[k]-1), {k,1,n}]. 7
1, 3, 7, 23, 121, 21, 173, 1597, 17927, 127469, 129317, 43619, 44081, 44521, 1033223, 13538159, 395369371, 132680013, 400467919, 402757063, 1214947859, 1221110939, 50305908619, 50529880549, 101470376303, 509322834499, 8691337402883 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) are squarefree except for n = 5, 14, 49, ... where squared prime factors are 11, 211, 479, ...

LINKS

Table of n, a(n) for n=1..27.

Eric Weisstein's World of Mathematics, Prime Sums.

FORMULA

a(n) = numerator(Sum_{k=1..n} 1/(prime(k)-1)).

a(n) = A078456(n) * A135212(n). - Alexander Adamchuk, Nov 23 2007

MATHEMATICA

Numerator[Table[Sum[1/(Prime[i]-1), {i, 1, n}], {n, 1, 50}]]

PROG

(PARI) a(n) = numerator(sum(k=1, n, 1/(prime(k)-1))); \\ Michel Marcus, Oct 02 2016

CROSSREFS

Cf. A119686, A006093, A000040.

Cf. A135212, A078456.

Sequence in context: A096318 A268140 A133788 * A145938 A048721 A113824

Adjacent sequences:  A120268 A120269 A120270 * A120272 A120273 A120274

KEYWORD

frac,nonn

AUTHOR

Alexander Adamchuk, Jul 01 2006

STATUS

approved

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Last modified February 23 04:57 EST 2018. Contains 299473 sequences. (Running on oeis4.)