A217068 Least number m such that phi(m-6n) = phi(m) = phi(m+6n) and m is not divisible by n.

7991, 4096740829, 651, 25056, 23973, 41526, 1302, 5005333, 8175, 504, 1953, 2919396, 13737, 1054, 2257, 1708, 11521, 22313, 16350, 123098, 1008, 1584, 3906, 1887, 89027, 5335754, 27474, 59550082, 2108, 1344, 4514, 1512, 3416, 2925, 5859, 494379, 44626, 1586993, 8557

Offset

2,1

Comments

a(n) has been computed by Donovan Johnson up to 200, but no values were found below 2*10^11 for n=41, 67, 113, 149, 157, 181.

Links

Table of n, a(n) for n=2..40.

F. Firoozbakht, Puzzle 466. phi(n-1)=phi(n)=phi(n+1), in C. Rivera's Primepuzzles.

S. W. Graham, J. J. Holt and C. Pomerance, On the solutions to phi(n) = phi(n+k) Number Theory in Progress, K. Gyory, H. Iwaniec, and J. Urbanowicz, eds., vol. 2, de Gruyter, Berlin and New York, 1999, pp. 867-882.

Donovan Johnson and Michel Marcus, a(n) for n=2 to 200, with missing terms shown as 0.

Crossrefs

Cf. A000010, A217006.

Sequence in context: A233730 A175507 A126893 * A043614 A223285 A223482

Adjacent sequences: A217065 A217066 A217067 * A217069 A217070 A217071

Keyword

nonn

Author

Michel Marcus, Sep 26 2012

Status

approved