A153789 First differences of harmonic (or Ore) numbers A001599.

5, 22, 112, 130, 226, 176, 966, 1332, 3230, 1928, 62, 10410, 20, 9226, 2394, 2520, 23100, 49804, 12136, 49600, 6200, 63910, 4550, 90580, 27720, 179040, 156120, 30660, 27300, 197496, 138294, 332010, 118440, 638820, 50960, 60760, 166740

Offset

1,1

Links

Muniru A Asiru, Table of n, a(n) for n = 1..71

Mathematica

a := Select[Range[1000000], IntegerQ[HarmonicMean[Divisors[#]]] &]; Table[Part[a, n + 1] - Part[a, n], {n, 1, 30}] (* G. C. Greubel, Aug 29 2016 *)

Prog

(GAP) H:=Concatenation([1], Filtered([2, 4..3*10^6], n->IsInt(n*Tau(n)/Sigma(n))));;
a:=List([1..Length(H)-1], i->H[i+1]-H[i]);; Print(a); # Muniru A Asiru, Dec 23 2018
(Python)
from numpy import diff
from sympy import divisor_sigma as sigma
def ore(n): return (n*sigma(n, 0))%sigma(n, 1) == 0
print(diff(list(filter(ore, range(1, 9000))))) # Michael S. Branicky, May 22 2021

Crossrefs

Cf. A001599.

Sequence in context: A267241 A162271 A164593 * A213167 A355398 A005033

Adjacent sequences: A153786 A153787 A153788 * A153790 A153791 A153792

Keyword

nonn

Author

Omar E. Pol, Jan 20 2009

Extensions

More terms from R. J. Mathar, Feb 19 2009

Status

approved