OFFSET
1,1
COMMENTS
a(n) is even for n=2,18,24,44,67 while a(n) is odd for other values of n < 85.
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
FORMULA
Conjecture: there is a constant 2 < c < 2.1 such that a(n)=n^c asymptotically.
MATHEMATICA
Flatten[Position[Partition[EulerPhi[Range[3400]], 3, 1], _?(#[[1]]== #[[3]]&), 1, Heads->False]]+1 (* Harvey P. Dale, Apr 18 2018 *)
PROG
(PARI) { n=0; a=1; for (m=1, 10^10, while (1, a++; if (eulerphi(a+1) == eulerphi(a-1), break)); write("b066812.txt", n++, " ", a); if (n==1000, return) ) } \\ Harry J. Smith, Mar 29 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 20 2002
EXTENSIONS
Corrected by Ralf Stephan, Feb 20 2004
STATUS
approved