A085127 Multiples of 4 which are members of A002473. Or multiples of 4 with the largest prime divisor < 10.

4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 48, 56, 60, 64, 72, 80, 84, 96, 100, 108, 112, 120, 128, 140, 144, 160, 168, 180, 192, 196, 200, 216, 224, 240, 252, 256, 280, 288, 300, 320, 324, 336, 360, 384, 392, 400, 420, 432, 448, 480, 500, 504, 512, 540, 560, 576

Offset: 1

Author

Amarnath Murthy, Jul 06 2003

Keywords

• easy
• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A008586 and A002473.

Cf. A085125, A085126, A085128, A085129, A080194, A085131, A085132.

Programs

Maple

N:= 1000: # to get all terms <= N
sort([seq(seq(seq(seq(2^a*3^b*5^c*7^d, d=0..floor(log[7](N/(2^a*3^b*5^c)))),c=0..floor(log[5](N/(2^a*3^b)))), b=0..floor(log[3](N/2^a))), a=2..floor(log[2](N)))]); # Robert Israel, Mar 18 2018

Mathematica

Select[4Range[150],Last[FactorInteger[#]][[1]]<10&] (* Harvey P. Dale, Aug 24 2011 *)

Formula

a(n) = 4*A002473(n). - Robert Israel, Mar 18 2018

Sum_{n>=1} 1/a(n) = 35/32. - Amiram Eldar, Sep 23 2024

Extensions

More terms from David Wasserman, Jan 28 2005

Offset changed by Robert Israel, Mar 18 2018