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A198044
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a(n) is the smallest number k such that d(1)*1! + d(2)*2! + ... + d(p)*p! = n, where d(1),...,d(p) are the decimal digits of k, or 0 if no such number exists.
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4
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1, 2, 3, 4, 5, 6, 7, 8, 9, 24, 15, 25, 16, 26, 17, 27, 18, 28, 19, 29, 39, 49, 59, 69, 79, 89, 99, 214, 124, 224, 105, 205, 115, 215, 125, 225, 106, 206, 116, 216, 126, 226, 107, 207, 117, 217, 127, 227, 108, 208, 118, 218, 128, 228, 109, 209, 119, 219, 129
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OFFSET
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1,2
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COMMENTS
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If 9*A007489(d) < n < (d+1)! then a(n)=0. The least d for which 9*A007489(d)+1<(d+1)! is 10, so a(n)=0 for 36341217 < n < 39916800. - Robert Israel, Aug 16 2020
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LINKS
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EXAMPLE
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a(59) = 129 because 1*1! + 2*2! + 9*3! = 1+4+54 = 59.
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MAPLE
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for n from 1 to 70 do :i:=0:for nn from 1 to 1000 while(i=0) do:l:=length(nn):n0:=nn:s:=0:for m from l by -1 to 1 do:q:=n0:u:=irem(q, 10):v:=iquo(q, 10):n0:=v :s:=s+u*m!:od: if s=n then i:=1:printf(`%d, `, nn):else fi:od:od:
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MATHEMATICA
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Table[k = 1; While[d = IntegerDigits[k]; s = Sum[d[[i]] i!, {i, Length[d]}]; s != n, k++]; k, {n, 100}] (* T. D. Noe, Oct 20 2011 *)
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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