

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
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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



