

A182273


Starting with 1, smallest integer not having a zero and not yet in the sequence such that two neighboring digits of the sequence multiply to a composite.


0



1, 4, 2, 3, 5, 6, 7, 8, 9, 14, 16, 18, 19, 22, 23, 24, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84
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OFFSET

1,2


COMMENTS

The number after 1 has to be 4, because the product 1*4 must be composite.
Then 2 is OK, because 4*2 = 8 is composite.
Then 3, because 2*3 = 6 is composite, and so on.
Note that 14 is the term after 9 because 10 is now the smallest candidate, but 10 has a 0 digit, 11 consists of two unit digits, and 12 and 13 have digit products 2 and 3, which are prime.  T. D. Noe, Apr 25 2012


LINKS

Table of n, a(n) for n=1..67.


CROSSREFS

Cf. A182272.
Sequence in context: A228047 A188543 A182272 * A166016 A213196 A275104
Adjacent sequences: A182270 A182271 A182272 * A182274 A182275 A182276


KEYWORD

nonn,base,easy,nice


AUTHOR

Jim Nastos and Eric Angelini, Apr 22 2012


STATUS

approved



