A073545 Least k such that 1/tau(k) + 1/tau(k+1) + 1/tau(k+2) + ... + 1/tau(k+n) is equal to 1 (where tau(k)=A000005(k) is the number of divisors of k).

1, 2, 6, 25, 54, 243, 1204, 3549, 19544, 81829, 104663, 663490, 743764, 7925355, 15376922, 39462786, 201432540, 1187707803, 3034296474, 8657654859, 48511905236, 154669032693, 123533546264

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Example

a(2)=6 because 1/tau(6)+1/tau(7)+1/tau(8) = 1/4+1/2+1/4 = 1.

Mathematica

a[n_] := For[k=1, True, k++, If[Sum[1/DivisorSigma[0, k+i], {i, 0, n}]==1, Return[k]]]
k = 1; Table[While[Sum[1/DivisorSigma[0, k + i], {i, 0, n}] != 1, k++]; k, {n, 0, 12}] (* Jayanta Basu, Jul 01 2013 *)

Crossrefs

Cf. A000005.

Sequence in context: A173609 A294945 A353363 * A103063 A220191 A030228

Adjacent sequences: A073542 A073543 A073544 * A073546 A073547 A073548

Keyword

nonn,more

Author

Benoit Cloitre, Aug 27 2002

Extensions

Edited by Dean Hickerson, Sep 03 2002

2 more terms from Ryan Propper, Sep 04 2005

a(14)-a(22) from Donovan Johnson, Jun 23 2010

Status

approved