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A103176
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Prime with subscript=sigma(n), if p[sigma(n)]-p[phi(n)]=A067161(n)-A048848(n)=6, where p(j)=j-th prime.
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0
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3, 19, 43, 113, 463, 619, 863, 1789, 2273, 2383, 4519, 4789, 4937, 5443, 5507, 5653, 8237, 10459, 13007, 13697, 16063, 16453, 17389, 18313, 18919, 20903, 21193, 21319, 21383, 23567, 24109, 25309, 26267, 27947, 28283, 29573, 30559, 31183, 31517
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Conjectured: In all cases sigma(n)-phi(n)=2, i.e. n is a prime number.
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EXAMPLE
| n=3719,sigma[n]=3720,phi(n)=3718, a(n)=p[sigma(n)]=34847.
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MAPLE
| Do[g=n; a=Prime[u=DivisorSigma[1, n]]; b=Prime[w=EulerPhi[n]]; s=a-b; If[Equal[s, 6], Print[{n, a, b, u, w, u-w}]; ta=Append[ta, a]], {n, 1, 10000}] ta=Delete[ta, 1]
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CROSSREFS
| Cf. A067161, A048848, A000020, A000203.
Sequence in context: A103145 A100694 A146664 * A028880 A162905 A201875
Adjacent sequences: A103173 A103174 A103175 * A103177 A103178 A103179
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KEYWORD
| nonn,uned
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Mar 02 2005
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