OFFSET
1,1
COMMENTS
Many terms are just twice a prime: 6, 22, 46, 58, 62, 94,....
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..1000
EXAMPLE
The number 138 has trajectory {138, 45, 25, 21, 13}, which is conjecturally the last number that terminates with 13 = prime(6). Hence a(6) = 138.
MATHEMATICA
t = Table[NestWhileList[EulerPhi[#] + 1 &, n, UnsameQ, All][[-1]], {n, 100000}]; Table[Position[t, p][[-1]], {p, Prime[Range[53]]}]
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Oct 16 2013
STATUS
approved