A064404 When the numerator - denominator (A064169) in n-th harmonic number is prime.

3, 4, 6, 7, 10, 19, 20, 26, 30, 31, 33, 40, 63, 85, 92, 100, 126, 131, 185, 196, 200, 204, 242, 246, 272, 274, 282, 379, 553, 572, 654, 777, 902, 1100, 1216, 1225, 1236, 1316, 1413, 1658, 1943, 2077, 2086, 2744, 2746, 2856, 2860, 3518, 3718, 4184, 4189, 4363

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..92

Henri Lifchitz and Renaud Lifchitz, PRP Records

Mathematica

s = 1; Do[ m = n; s = s + 1/n; If[ PrimeQ[ Numerator[ s ] - Denominator[ s ] ], Print[ n ] ], {n, 2, 2500} ]
hnoQ[n_]:=Module[{h=HarmonicNumber[n]}, PrimeQ[Numerator[h]-Denominator[ h]]]; Select[Range[5000], hnoQ]  (* Harvey P. Dale, May 23 2012 *)

Prog

(PARI) for(n=2, 300, if(isprime(lcm(n!, sum(k=2, n, 1/k))/n!), print1(n, ", "))); \\ Arkadiusz Wesolowski, Oct 13 2011

Crossrefs

Cf. A064169.

Sequence in context: A024912 A108588 A194095 * A294488 A364341 A335059

Adjacent sequences: A064401 A064402 A064403 * A064405 A064406 A064407

Keyword

nonn

Author

Robert G. Wilson v, Sep 28 2001

Extensions

More terms from Arkadiusz Wesolowski, Oct 13 2011

Status

approved