A051539 a(n) is the least common multiple of {1, 5, 9, 13, 17, ..., 4n+1} (A016813).

1, 5, 45, 585, 9945, 69615, 348075, 10094175, 111035925, 4108329225, 168441498225, 168441498225, 1179090487575, 62491795841475, 1187344120988025, 72427991380269525, 72427991380269525, 1665843801746199075, 121606597527472532475, 121606597527472532475

Offset: 0

Author

Asher Auel

Keywords

• easy
• nice
• nonn

Comments

This sequence coincides with sequence A097328 of denominators of 1 + 1/5 + 1/9 + 1/13 + ... + 1/(4n+1) iff n < 12. - T. D. Noe, Aug 04 2004

Examples

			a(3) = LCM {1, 5, 9, 13} = 585.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..866 (first 201 terms from T. D. Noe)
• Index entries for sequences related to lcm's

Crossrefs

Cf. A016813, A075136, A074598, A097329.

Programs

Magma

k:=77; [Lcm([h: h in [1..j by 4]]): j in [1..k by 4]];  // Bruno Berselli, May 03 2011

Mathematica

Table[ Apply[ LCM, Join[{1}, Table[1 + 4i, {i, 0, n}]]], {n, 0, 19}]
nn=20;Table[LCM@@Take[4Range[0,nn-1]+1,n],{n,nn}] (* Harvey P. Dale, Jul 04 2011 *)
Table[LCM@@NestList[#+4&,1,n],{n,0,20}] (* Harvey P. Dale, Nov 21 2016 *)

PARI

a(n)=lcm(vector(n,i,4*n+1)) \\ Charles R Greathouse IV, Feb 09 2017

Extensions

Edited by Robert G. Wilson v, Aug 27 2002

a(16) corrected by T. D. Noe, Feb 08 2008