A336743 a(n) is the product of the first n positive evil numbers.

1, 3, 15, 90, 810, 8100, 97200, 1458000, 24786000, 446148000, 8922960000, 205228080000, 4925473920000, 132987795840000, 3856646079360000, 115699382380800000, 3818079618566400000, 129814707031257600000, 4673329453125273600000, 182259848671885670400000

Offset: 0

Author

Jamie Robert Creasey, Sep 26 2020

Keywords

• nonn
• base

Comments

Despite 0 appearing in the evil numbers, it is excluded here for obvious reasons.

This sequence features a mixture of odious and evil numbers, demonstrated in terms such as a(5) and a(8), where 8100 is evil but 24768000 is odious. As such, this shows that despite doubling preserving evilness, this is untrue for all multipliers.

Examples

			a(3) = 3*5*6 = 90.
a(8) = 3*5*6*9*10*12*15*17 = 24786000.
		

Crossrefs

Cf. A000142, A000069 (odious), A001969 (evil).

Programs

Mathematica

FoldList[Times, 1, Select[Range[40], EvenQ @ DigitCount[#, 2, 1] &]] (* Amiram Eldar, Sep 26 2020 *)

Formula

a(n) = Product_{k=2, n+1} A001969(k). - Michel Marcus, Sep 27 2020