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A068185
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Number of ways writing n^n as a product of decimal digits of some other number which has no digits equal to 1.
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1
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0, 2, 3, 81, 1, 102136, 1, 1389537, 317811, 4972825, 0, 12718670252691776, 0, 4506838380, 11472991008, 53560898629395777, 0, 514875062240230100091396, 0, 164997736300578242823300, 241098942106440, 0, 0, 3203410440031870942324022423896806853153460, 1, 0, 61305790721611591
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n)= 0 when n has prime-factor larger than 7 [so A067734(n)=0] or when n is in A068191, i.e. not in A002473.
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FORMULA
| a(n) = A067734(n^n) = A067734(A000312(n))
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EXAMPLE
| n=1 has no solution; a(2)=A000073(6)=2 with {4,22} solutions; a(3)=A067734(27)=3=Fibonacci[4]; n=5 and n=7, n^n has single prime factor of which any true multiple have 2 digits so 55555 and 7777777 are the only solutions, so a(5)=a(7)=1; a(4)=A067734(256)=81=A000073(10); a(8)=A067734(2^24)=A000073(26)=1389537; n=9 a(9)=A067734(3^27)=Fibonacci(28)=A000045(28)=317811.
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CROSSREFS
| Cf. A000045, A000073, A000312, A001222, A002473, A067734, A068183-A068187, A068189-A068191.
Sequence in context: A176290 A091825 A166091 * A037391 A037427 A042549
Adjacent sequences: A068182 A068183 A068184 * A068186 A068187 A068188
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KEYWORD
| base,nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Feb 19 2002
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EXTENSIONS
| Edited By Henry Bottomley (se16(AT)btinternet.com), Feb 26 2002.
Edited and extended by Max Alekseyev (maxale(AT)gmail.com), Sep 19 2009
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