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A229323
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Composite squarefree numbers n such that p - tau(n) divides n - phi(n), where p are the prime factors of n, tau(n) = A000005(n) and phi(n) = A000010(n).
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2
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6, 10, 15, 21, 42, 28101, 38505, 5298186, 8022111, 28231629, 36367086, 98671659, 132798279, 163143714, 201713946, 251860911, 434246667, 537424773, 968870877, 999640581, 1495625721, 1548129363, 3338717307, 3836384682, 6316358811, 6982412973
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OFFSET
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1,1
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COMMENTS
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Subsequence of A120944.
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LINKS
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Table of n, a(n) for n=1..26.
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EXAMPLE
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Prime factors of 28101 are 3, 17, 19, 29 and tau(28101) = 16, phi(28101) = 16128. 28101 - 16128 = 11973 and 11973 / (3 - 16) = -921, 11973 / (17 - 16) = 11973, 11973 / (19 - 16) = 3991, 11973 / (29 - 16) = 921.
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MAPLE
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with (numtheory); P:=proc(q) global a, b, c, i, ok, p, n;
for n from 2 to q do if not isprime(n) then a:=ifactors(n)[2]; ok:=1;
for i from 1 to nops(a) do if a[i][2]>1 or a[i][1]=tau(n) then ok:=0; break;
else if not type((n-phi(n))/(a[i][1]-tau(n)), integer) then ok:=0; break; fi; fi; od; if ok=1 then print(n); fi; fi; od; end: P(6*10^9);
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CROSSREFS
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Cf. A000005, A000010, A228299-A228302, A229274-A229276, A229321, A229322, A229324.
Sequence in context: A333747 A124000 A229321 * A068443 A113940 A315280
Adjacent sequences: A229320 A229321 A229322 * A229324 A229325 A229326
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KEYWORD
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nonn
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AUTHOR
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Paolo P. Lava, Sep 20 2013
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EXTENSIONS
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a(9)-a(27) from Giovanni Resta, Sep 20 2013
First term deleted by Paolo P. Lava, Sep 23 2013
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STATUS
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approved
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