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A276654
a(n) = the smallest number k>1 such that floor(Sum_{p|k} 0.p) = n where p runs through the prime divisors of k.
6
2, 21, 2905, 281785, 47740490, 9178864590, 8533159052845, 1817562878255985, 1801204812351681135, 787408225243814333670
OFFSET
0,1
COMMENTS
Here 0.p means the decimal fraction obtained by writing p after the decimal point, e.g. 0.11 = 11/100.
The first few values of Sum_{p|n} 0.p are: 1/5, 3/10, 1/5, 1/2, 1/2, 7/10, 1/5, 3/10, 7/10, ...
Subsequence of A005117. - Chai Wah Wu, Sep 15 2016
EXAMPLE
Number 2905 is the smallest number k with floor(Sum_{p|k} 0.p) = 2; set of prime divisors of 2905: {5, 7, 83}; floor(Sum_{p|2905} 0.p) = 0.5 + 0.7 + 0.83 = floor(2.03) = 2.
MATHEMATICA
Table[k = 2; While[f = FactorInteger[k][[All, 1]];
Floor[Total[f*10^-IntegerLength[f]]] != n, k++];
k, {n, 0, 3}] (* Robert Price, Sep 20 2019 *)
PROG
(Magma) A276654:=func<n|exists(r){k:k in[2..1000000] | Floor(&+[d / (10^(#Intseq(d))): d in PrimeDivisors(k)]) eq n}select r else 0>; [A276654(n): n in[0..3]]
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Jaroslav Krizek, Sep 11 2016
EXTENSIONS
a(4) from Michel Marcus, Sep 11 2016
a(5)-a(9) from Giovanni Resta, Aug 31 2019
STATUS
approved