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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 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: A299404 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 August 18 00:56 EDT 2019. Contains 326059 sequences. (Running on oeis4.)