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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

%I

%S 2,21,2905,281785,47740490

%N 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.

%C Here 0.p means the decimal fraction obtained by writing p after the decimal point, e.g. 0.11 = 11/100.

%C 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, ...

%C Subsequence of A005117. - _Chai Wah Wu_, Sep 15 2016

%e 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.

%o (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]]

%Y Cf. A005117, A276513, A276651, A276652, A276653, A276655.

%K nonn,base,more

%O 0,1

%A _Jaroslav Krizek_, Sep 11 2016

%E a(4) from _Michel Marcus_, Sep 11 2016

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Last modified July 18 21:25 EDT 2019. Contains 325144 sequences. (Running on oeis4.)