A156237 Smallest hexagonal number with n distinct prime factors.

6, 66, 630, 7140, 103740, 1272810, 56812470, 1722580860, 48098217090, 1850186768430, 139261952960130, 17743036637876550, 741902728913225880, 21549201398378163510, 2378522762792139793830, 351206814022419685159830

Offset

2,1

Comments

a(18) <= 45781615623002935783197090. - Donovan Johnson, Feb 15 2012

Links

Table of n, a(n) for n=2..17.

Eric Weisstein's World of Mathematics, Hexagonal Numbers.

Example

a(9) = 1722580860 = 2^2*3*5*7*11*13*23*29*43. 1722580860 is the smallest hexagonal number with 9 distinct prime factors.

Mathematica

Module[{nn=167*10^5, c}, c={#, PrimeNu[#]}&/@PolygonalNumber[6, Range[nn]]; Table[ SelectFirst[ c, #[[2]]==n&], {n, 2, 12}]][[;; , 1]] (* The program generates the first 11 terms of the sequence. *) (* Harvey P. Dale, Jan 19 2024 *)

Crossrefs

Cf. A000384, A076551, A156236, A156238, A156239.

Sequence in context: A227164 A043041 A243719 * A119142 A119091 A119100

Adjacent sequences: A156234 A156235 A156236 * A156238 A156239 A156240

Keyword

nonn

Author

Donovan Johnson, Feb 07 2009

Status

approved