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A131195
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Nonprime record values of Euler's totient function (A000010): 1 and composite n such that phi(n) is greater than all smaller composites.
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0
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1, 4, 8, 9, 15, 21, 25, 35, 49, 65, 77, 85, 91, 115, 119, 121, 143, 161, 169, 187, 203, 209, 221, 247, 253, 287, 289, 319, 323, 341, 361, 391, 403, 437, 451, 473, 481, 493, 517, 527, 529, 583, 589, 611, 629, 649, 667, 689, 697, 703, 713, 731, 767, 779, 799, 817
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Since phi(p) = p - 1, allowing prime numbers in this sequence would make it A006005, the primes with a 1 replacing the initial 2.
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EXAMPLE
| a(3) = 8 because phi(8) = 4, which is greater than phi(4) = phi(6) = 2. (phi(5) = 4 and phi(7) = 6 are ignored because 5 and 7 are prime).
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MATHEMATICA
| htcList = {1}; i = 4; currMax = 1; searchMax = 1000; While[i < searchMax, If[Not[PrimeQ[i]] && EulerPhi[i] > currMax, htcList = {htcList, i}; currMax = EulerPhi[i]]; i++ ]; Flatten[htcList]
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CROSSREFS
| Cf. A000010, A000040.
Sequence in context: A023886 A158337 A161542 * A020217 A141066 A018196
Adjacent sequences: A131192 A131193 A131194 * A131196 A131197 A131198
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KEYWORD
| easy,nonn,changed
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AUTHOR
| Alonso Delarte (alonso.delarte(AT)gmail.com), Oct 20 2007
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