The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A139770 Smallest number having at least as many divisors as n. 5
 1, 2, 2, 4, 2, 6, 2, 6, 4, 6, 2, 12, 2, 6, 6, 12, 2, 12, 2, 12, 6, 6, 2, 24, 4, 6, 6, 12, 2, 24, 2, 12, 6, 6, 6, 36, 2, 6, 6, 24, 2, 24, 2, 12, 12, 6, 2, 48, 4, 12, 6, 12, 2, 24, 6, 24, 6, 6, 2, 60, 2, 6, 12, 24, 6, 24, 2, 12, 6, 24, 2, 60, 2, 6, 12, 12, 6, 24, 2, 48, 12, 6, 2, 60, 6, 6, 6, 24, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Similar to A140635, except that a(n) is allowed to have more divisors than n. a(n) <= n for all n. Moreover, a(n) = n if and only if n belongs to A061799 (or equivalently A002182). When n is prime, a(n) = 2. - Michel Marcus, Jun 14 2013 For numbers k such that a(k) and A140635(k) are not equal see A365263. - Michel Marcus, Aug 31 2023 LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A061799(A000005(n)). EXAMPLE 16 has 5 divisors; smallest number with at least 5 divisors is 12 with 6 divisors, thus a(16) = 12. MATHEMATICA a139770[n_] := NestWhile[#+1&, 1, DivisorSigma[0, n]>DivisorSigma[0, #]&] a139770[{m_, n_}] := Map[a139770, Range[m, n]] a139770[{1, 89}] (* Hartmut F. W. Hoft, Jun 13 2023 *) PROG (PARI) a(n) = {nd = numdiv(n); for (i=1, n-1, if (numdiv(i) >= nd, return (i)); ); return (n); } \\ Michel Marcus, Jun 14 2013 (Python) from sympy import divisor_count as d def a(n): x=d(n) m=1 while True: if d(m)>=x: return m else: m+=1 # Indranil Ghosh, May 27 2017 CROSSREFS Cf. A000005, A002182, A061799, A140635, A365263. Sequence in context: A122457 A319410 A337174 * A140635 A283465 A283466 Adjacent sequences: A139767 A139768 A139769 * A139771 A139772 A139773 KEYWORD nonn AUTHOR J. Lowell, May 20 2008 EXTENSIONS Edited and extended by Ray Chandler, May 24 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 24 02:58 EST 2024. Contains 370288 sequences. (Running on oeis4.)