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A107221 Numbers such that sum of digits is 7 and product of digits is 8. +0
1
124, 142, 214, 241, 412, 421, 1222, 2122, 2212, 2221 (list; graph; listen)
OFFSET

1,1

COMMENT

Sequence is finite.

There are no other terms. Proof. From the fact that the product of the digits is 8, we can conclude that each number contains either three '2's or a '2' and a '4' or a single '8' together with arbitrary many '1's. In the first case there has to be exactly one '1', otherwise the sum wouldn't be 7. This gives the numbers 1222, 2122, 2212, 2221. In the second case, there can also be only one '1', this yields the numbers 124, 142, 214, 241, 412, 421. The third case is not possible because 8 is for itself already bigger than 7. All those terms are listed, hence the sequence is complete. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 07 2007

CROSSREFS

Sequence in context: A080537 A030492 A031203 this_sequence A056085 A129010 A133606

Adjacent sequences: A107218 A107219 A107220 this_sequence A107222 A107223 A107224

KEYWORD

nonn,fini,full

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), May 13 2005

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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