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A067791
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Smallest multidigit prime such that the sum of the squares of its digits is equal to n times the product of its digits, or 0 if no such prime exists.
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0
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11353, 11, 211, 1111116211, 11411, 511111, 1111111111111111111111111111213, 11111117, 111111181, 1111111111111111111711, 2111111111111111111, 111111111111111121111, 1111111111111111111111141111111111111, 1111111111111111211111111, 111111111111111111111111111111111511111111111111111, 1111111111111111111111111111111111111141111111111, 1111111111111111211111111111111, 0, 1111111111111111111, 0, 111111211111111111111111111111111111111, 0, 11111111111111111111111
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Sum(xi^2)=n*Prod(xi) where xi is the i-th digit of a prime in base 10. The zero has been entered for those n values such that no solution has been found up to 10^7.
No more terms up to 4.4e11.
a(n) > (10^52-1)/9 for n = 18, 20, and 22. - Donovan Johnson
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CROSSREFS
| Sequence in context: A178583 A178589 A179917 * A067779 A202377 A185768
Adjacent sequences: A067788 A067789 A067790 * A067792 A067793 A067794
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KEYWORD
| nonn,base,more
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AUTHOR
| Felice Russo (frusso(AT)micron.com), Feb 06 2002
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EXTENSIONS
| a(8) and a(9) corrected by Charles R Greathouse IV, Nov 19 2010.
a(4), a(7), a(10)-a(17), a(19), a(21) and a(23) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 20 2010
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