This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A137518 a(1)=2. For n>=2, a(n) = smallest integer > a(n-1) that has the same number of divisors as n has. 4
 2, 3, 5, 9, 11, 14, 17, 21, 25, 26, 29, 32, 37, 38, 39, 81, 83, 92, 97, 98, 106, 111, 113, 114, 121, 122, 123, 124, 127, 128, 131, 147, 155, 158, 159, 196, 197, 201, 202, 222, 223, 230, 233, 236, 242, 247, 251, 272, 289, 292, 295, 316, 317, 318, 319, 322, 323 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Starting the sequence at a(1)=1 instead would lead to a(n) = n for all positive integers n. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA a = {2}; Do[i = a[[ -1]] + 1; While[ ! Length[Divisors[i]] == Length[Divisors[n]], i++ ]; AppendTo[a, i], {n, 2, 80}]; a (* Stefan Steinerberger, Apr 26 2008 *) nxt[{a_, n_}]:=Module[{k=a+1, div=DivisorSigma[0, n+1]}, While[div != DivisorSigma[ 0, k], k++]; {k, n+1}]; Transpose[NestList[nxt, {2, 1}, 60]] [[1]] (* Harvey P. Dale, May 28 2014 *) CROSSREFS Sequence in context: A215779 A140329 A163292 * A137509 A014109 A102940 Adjacent sequences:  A137515 A137516 A137517 * A137519 A137520 A137521 KEYWORD nonn AUTHOR Leroy Quet, Apr 24 2008 EXTENSIONS More terms from Stefan Steinerberger, Apr 26 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 15 14:37 EST 2019. Contains 329999 sequences. (Running on oeis4.)