OFFSET
1,1
COMMENTS
Note that a(3) = (5 * 7 * 11 * 13 * 17 * 19 * 23 * ... * 149 - 1) / 6. When 2n is the product of distinct small primes, a(n) is very large; e.g. Martin shows that a(15) is a 1116-digit number. The large values of a(n) were computed quickly using a backtracking algorithm.
LINKS
Greg Martin, The smallest solution of phi(30n+1) < phi(30n) is ..., arXiv:math/0904025, 1998.
D. J. Newman, Euler's phi function on arithmetic progressions, Amer. Math. Monthly, Vol. 104, No. 3 (Mar. 1997), pp. 256-257.
Herman te Riele, On the size of solutions of the inequality phi(ax+b) < phi(ax)
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Dec 09 2003
STATUS
approved