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Search: id:A125309
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| A125309 |
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Numbers n such that twice the sum of the prime factors of n equals the product of the digits of n. |
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+0
1
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| 4, 25, 76, 125, 187, 255, 437, 629, 1152, 1276, 1298, 1352, 1617, 1668, 2337, 3363, 3618, 4116, 4439, 5891, 6432, 8279, 11178, 13125, 14144, 14812, 14824, 18647, 22165, 22466, 23472, 24727, 24743, 25631, 26128, 32978, 37329, 42983, 48442
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Number of terms less than 10^n: 1, 3, 8, 22, 48, 103, 230, 611, ...; number of odd terms less than 10^n: 0, 1, 6, 12, 21, 51, 120, 331, ..., . - Robert G. Wilson v (rgwv(at)rgwv.com), Dec 12 2006
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EXAMPLE
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Prime factors of 76 are 2 and 19; twice their sum is 42 which the product of 7 and 6 - the digits of 76.
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MATHEMATICA
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Select[Range[2, 20000], Times @@ IntegerDigits[ # ] == 2 Plus @@ Transpose[FactorInteger[ # ]][[1]] &]
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CROSSREFS
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Similar to A067173 = numbers n such that the sum of the prime factors of n equals the product of the digits of n.
Adjacent sequences: A125306 A125307 A125308 this_sequence A125310 A125311 A125312
Sequence in context: A016790 A065733 A077205 this_sequence A041991 A027764 A095669
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KEYWORD
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base,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Dec 10 2006
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 12 2006
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