A136684 Numbers k such that A120296(k) is prime.

3, 5, 8, 11, 20, 38, 61, 65, 71, 80, 83, 93, 233, 704, 1649, 2909, 3417, 3634, 9371

Offset

1,1

Comments

A120296(k) = Numerator of Sum_{j=1..k} (-1)^(j+1)/j^4.

Links

Table of n, a(n) for n=1..19.

Eric Weisstein's World of Mathematics, Harmonic Number

Mathematica

Do[ f=Numerator[ Sum[ (-1)^(k+1)*1/k^4, {k, 1, n} ] ]; If[ PrimeQ[f], Print[ {n, f} ] ], {n, 1, 100} ]
Select[Range[1000], PrimeQ[Numerator[Sum[(-1)^(k+1) 1/k^4, {k, #}]]]&] (* Harvey P. Dale, Aug 28 2012 *)

Crossrefs

Cf. A058313, A119682, A136675, A120296, A136676, A136677.

Cf. A001008, A007406, A007408, A007410, A099828, A103345.

Cf. A136681, A136682, A136683, A136685, A136686.

Sequence in context: A180619 A196204 A220483 * A215751 A115888 A143814

Adjacent sequences: A136681 A136682 A136683 * A136685 A136686 A136687

Keyword

nonn,more

Author

Alexander Adamchuk, Jan 16 2008

Extensions

More terms from Harvey P. Dale, Aug 28 2012

a(15)-a(19) from Robert Price, Apr 23 2019

Status

approved