A128647 a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).

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

Offset: 1

Author

Alexander Adamchuk, Mar 18 2007

Keywords

• frac
• nonn

Comments

Numbers m such that A128648(m) = A128646(n) are listed in A128649.

Links

• Eric Weisstein's World of Mathematics, Prime sums

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.

Programs

Mathematica

Table[Numerator[Sum[(-1)^(k+1)*1/(Prime[k]-1),{k,1,n}]],{n,1,36}]

Formula

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