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

1,1

Comments

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

Links

Table of n, a(n) for n=1..45.

Eric Weisstein's World of Mathematics, Harmonic Number

Mathematica

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

Crossrefs

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

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

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

Sequence in context: A041157 A178356 A042785 * A107467 A191425 A155881

Adjacent sequences: A136679 A136680 A136681 * A136683 A136684 A136685

Keyword

nonn

Author

Alexander Adamchuk, Jan 16 2008

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

Status

approved