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 A128647 a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)). 3
 1, 1, 3, 7, 41, 3, 53, 437, 5167, 34189, 36037, 3833, 3987, 11521, 274223, 3458639, 103063291, 100392623, 34273501, 33510453, 308270747, 302107667, 12626774467, 12402802537, 25216220279, 124110148411, 2142721739387, 111888942151111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers m such that A128648(m) = A128646(n) are listed in A128649. LINKS Table of n, a(n) for n=1..28. Eric Weisstein's World of Mathematics, Prime sums FORMULA a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)). MATHEMATICA Table[Numerator[Sum[(-1)^(k+1)*1/(Prime[k]-1), {k, 1, n}]], {n, 1, 36}] CROSSREFS Cf. A128648 (denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1))). Cf. A120271 (numerator(Sum_{k=1..n} 1/(prime(k)-1))). Cf. A128646, A128649, A119686, A006093, A000040. Sequence in context: A019024 A135071 A096219 * A071730 A058815 A333649 Adjacent sequences: A128644 A128645 A128646 * A128648 A128649 A128650 KEYWORD frac,nonn AUTHOR Alexander Adamchuk, Mar 18 2007 STATUS approved

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Last modified April 22 08:40 EDT 2024. Contains 371893 sequences. (Running on oeis4.)