A122152 Primes in A122150[n] = Numerator[ Sum[ (-1)^(k+1) * 1/2^Prime[k], {k,1,n} ] ].

5, 19, 327235662833, 578175370366880553282134492422436321419543414585625120508329411643068012549226892303, 39731908913255031966162449696446781074231732174358868548789339497630379824042353480418749055951

Offset

1,1

Comments

A122150[n] = Numerator[ Sum[ (-1)^(k+1) * 1/2^Prime[k], {k,1,n} ] ] begins {1,1,5,19,305,1219,19505,78019,1248305,79891519,319566077,20452228927,327235662833,...}. Indices of primes in A122150[n] are listed in A122151[n] = {3,4,13,60,66,75,175,...}.

Links

Table of n, a(n) for n=1..5.

Formula

a(n) = A122150[ A122151[n] ].

Mathematica

Do[f=Numerator[Sum[(-1)^(k+1)*1/2^Prime[k], {k, 1, n}]]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1000}]

Crossrefs

Cf. A122150, A122151, A122153.

Sequence in context: A278562 A013531 A357517 * A104314 A302662 A261545

Adjacent sequences: A122149 A122150 A122151 * A122153 A122154 A122155

Keyword

nonn

Author

Alexander Adamchuk, Aug 22 2006

Status

approved