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Search: id:A056774
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| A056774 |
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Composite n such that phi[n+2] = phi[n]+2. |
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+0
1
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| 6, 12, 14, 18, 20, 44, 62, 92, 116, 164, 212, 254, 332, 356, 452, 524, 692, 716, 764, 932, 956, 1004, 1124, 1172, 1436, 1676, 1724, 1772, 1964, 2036, 2372, 2564, 2612, 2636, 2732, 2876, 2972, 3044, 3236, 3644, 3812, 4052, 4076, 4124, 4196, 4412, 4892
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OFFSET
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1,1
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COMMENT
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Below 100000 no common composite solutions with Sigma[n+2]=Sigma[n]+2, while prime solutions are common.
Phi[x]+2=Phi[x+2] is equivalent to Cototient[x+2]=Cototient[x], so alos defines closest numbers with identical value of cototients(=A051953), either primes or composites.
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EXAMPLE
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n=254, Phi[254+2]=Phi[256]=128=Phi[254]+2=126+2
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CROSSREFS
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Cf. A000010, A001838, A055458, A015913-A015917, A050507, A054799.
Sequence in context: A105115 A136155 A136151 this_sequence A031405 A105773 A079946
Adjacent sequences: A056771 A056772 A056773 this_sequence A056775 A056776 A056777
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 17 2000
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