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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). 0
1, 2, 6, 25, 54, 243, 1204, 3549, 19544, 81829, 104663, 663490, 743764, 7925355, 15376922, 39462786, 201432540, 1187707803, 3034296474, 8657654859, 48511905236, 154669032693, 123533546264 (list; graph; refs; listen; history; text; internal format)
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: A086591 A173609 A294945 * 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

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Last modified July 24 20:26 EDT 2021. Contains 346273 sequences. (Running on oeis4.)