

A026453


a(n) = least positive integer > a(n1) and not equal to a(i)*a(j)2 for 1<=i<j<=n1.


11



1, 2, 3, 5, 6, 7, 9, 11, 14, 15, 17, 18, 21, 22, 23, 24, 27, 29, 30, 35, 36, 37, 38, 39, 41, 45, 47, 48, 50, 51, 54, 55, 57, 59, 60, 62, 63, 65, 66, 69, 71, 77, 78, 81, 84, 86, 87, 89, 90, 91, 93, 95, 99, 101, 102, 104, 105, 107, 110, 111
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OFFSET

1,2


LINKS

Ivan Neretin, Table of n, a(n) for n = 1..1000


EXAMPLE

After the terms 1, 2, 3, 5, 6, 7, we can get 8 from 2*5  2, but not 9 (11 is not a product of two distinct terms from {1, 2, 3, 5, 6, 7}), so a(7) = 9.  N. J. A. Sloane, Aug 06 2021


MATHEMATICA

a = {1, 2}; used = {a[[1]]*a[[2]]  2}; Do[k = a[[1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a  2]; AppendTo[a, k], {n, 3, 60}]; a (* Ivan Neretin, Mar 06 2016 *)


CROSSREFS

Similar sequences with different starting conditions: A026454 (1,3), A026455 (2,3), A026456 (1,4), A026457 (2,4), A026458 (3,4).
Related sequences with definition using any products (not necessarily distinct) and with various starting conditions: A026459 (1,2), A026460 (1,3), A026461 (2,3), A026462 (1,4), A026463 (2,4), A026464 (3,4).
Sequence in context: A347498 A023884 A135607 * A026455 A082984 A085717
Adjacent sequences: A026450 A026451 A026452 * A026454 A026455 A026456


KEYWORD

nonn


AUTHOR

Clark Kimberling


EXTENSIONS

Typos in definition corrected by N. J. A. Sloane, Aug 06 2021 at the suggestion of Harvey P. Dale.


STATUS

approved



