A144178 - OEIS

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A144178

a(n) = b(2n-1)*b(2n) where b(3n+1) = floor(n/9) + 2, b(3n+2) = (n mod 9) + 2, b(3n+3) = b(3n+1)*b(3n+2) for n >= 0.

4, 8, 18, 8, 16, 50, 12, 24, 98, 16, 32, 162, 20, 60, 12, 9, 27, 48, 15, 45, 108, 21, 63, 192, 27, 81, 300, 8, 32, 36, 16, 64, 100, 24, 96, 196, 32, 128, 324, 40, 200, 20, 15, 75, 80, 25, 125, 180, 35, 175, 320, 45, 225, 500, 12, 72, 54, 24, 144, 150, 36, 216, 294, 48, 288

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Old name was: (2*2=4, 2*3=6, 2*4=8, 2*5=10, 2*6=12, 2*7=14, 2*8=16, 2*9=18, 2*10=20, 3*2=6, ...) becomes (abs(2*2, 4*2, 3*6, 2*4, 8*2, 5*10, 2*6, 12*2, 7*14, 2*8, 16*2, 9*18, 2*10, 20*3, 2*6, ...)).

(..., 9*9=81, 9*10=90, 10*2=20, 10*3=30, 10*4=40, 10*5=50, 10*6=60, 10*7=70, 10*8=80, 10*9=90, 10*10=100, 11*2=22, ...) becomes

(abs(..., 9*9, 81*9, 10*90, 10*2, 20*10, 3*30, 10*4, 40*10, 5*50, 10*6, 60*10, 7*70, 10*8, 80*10, 9*90, 10*10, 100*11, 2*22, ...)).

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

2*2 = 4 = a(1),

4*2 = 8 = a(2),

3*6 = 18 = a(3),

2*4 = 8 = a(4),

8*2 = 16 = a(5),

5*10 = 50 = a(6), etc.

MATHEMATICA

Times @@@ Partition[Flatten@ Table[{n, k, n k}, {n, 2, 10}, {k, 2, 10}], 2, 2] (* Michael De Vlieger, Oct 24 2022 *)

PROG

(PARI) a(n) = my(k=ceil(n/27), r=n-27*(k-1), v=[]); for(i=2, 10, v=concat(v, [2*k, i, 2*k*i])); for(i=2, 10, v=concat(v, [2*k+1, i, (2*k+1)*i])); v[2*r-1] * v[2*r] \\ Jianing Song, Oct 24 2022

CROSSREFS

Cf. A144176, A144177.

Sequence in context: A119471 A145779 A252790 * A075558 A312824 A312825

Adjacent sequences: A144175 A144176 A144177 * A144179 A144180 A144181

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Nov 19 2008

EXTENSIONS

Corrected (a 175 replaced by 225) by R. J. Mathar, Apr 29 2010

New name from Jianing Song, Nov 01 2022

STATUS

approved