login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A249055 a(1)=0; the next term is always the product of the two smallest numbers not yet in the sequence and which have not yet been used. 1
0, 2, 12, 30, 56, 90, 143, 210, 272, 342, 420, 506, 600, 702, 812, 992, 1122, 1260, 1406, 1560, 1722, 1892, 2070, 2256, 2450, 2652, 2862, 3135, 3422, 3660, 3906, 4160, 4422, 4692, 4970, 5256, 5550, 5852, 6162, 6480, 6806, 7140, 7482, 7832, 8372, 8742, 9120, 9506, 9900 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Suggested by A075336 and A249406.

LINKS

Table of n, a(n) for n=1..49.

EXAMPLE

Start with a(1) = 0. The missing numbers are 1 2 3 4 5 6 ...

Multiply the first two, and we get 2, which is therefore a(2).

Cross 1, 2, and 1*2 = 2 off the missing list.

The first two missing numbers are now 3 and 4, so a(3) = 3*4 = 12.

Cross off 3,4,12 from the missing list.

Repeat!

MAPLE

M:=50; A:=[0]; miss:=[seq(n, n=1..M^2)]:

for n from 1 to M do t1:=miss[1]*miss[2]; A:=[op(A), t1];

miss:=[seq(miss[i], i=3..nops(miss))];

miss:=remove('x->x=t1', miss);

od:

A;

CROSSREFS

Cf. A075326, A000045, A249406, A000304, A000301.

Sequence in context: A067348 A002939 A118239 * A127118 A259127 A296257

Adjacent sequences:  A249052 A249053 A249054 * A249056 A249057 A249058

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Nov 01 2014

EXTENSIONS

Typo in definition corrected by Douglas Latimer, Nov 01 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 22 23:18 EDT 2018. Contains 316518 sequences. (Running on oeis4.)