A136682 Numbers k such that A119682(k) is prime.

2, 3, 5, 8, 23, 41, 47, 48, 49, 95, 125, 203, 209, 284, 323, 395, 504, 553, 655, 781, 954, 1022, 1474, 1797, 1869, 1923, 1934, 1968, 2043, 2678, 3413, 3439, 4032, 4142, 4540, 4895, 5018, 5110, 5194, 5357, 6591, 11504, 11949, 14084, 20365

Offset: 1

Author

Alexander Adamchuk, Jan 16 2008

Keywords

• nonn

Comments

A119682(k) = Numerator of Sum_{j=1..k} (-1)^(j+1)/j^2.

Links

• Eric Weisstein's World of Mathematics, Harmonic Number

Crossrefs

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

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

Cf. A136681, A136683, A136684, A136685, A136686.

Programs

Mathematica

Do[ f=Numerator[ Sum[ (-1)^(k+1)*1/k^2, {k,1,n} ] ]; If[ PrimeQ[f], Print[ {n,f} ] ], {n,1,125} ]

Extensions

a(12)-a(17) from Alexander Adamchuk, Apr 28 2008

a(18)-a(31) from Amiram Eldar, Mar 14 2019

a(32)-a(45) from Robert Price, Apr 14 2019