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

0,2

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.

Links

Table of n, a(n) for n=0..19.

Formula

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

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A185369 A024339 A319950 * A034954 A077783 A347319

Adjacent sequences: A336740 A336741 A336742 * A336744 A336745 A336746

Keyword

nonn,base

Author

Jamie Robert Creasey, Sep 26 2020

Status

approved