login
A185011
Numbers k such that P(k^2+1) < P((k+1)^2+1) where P(n) (A006530) is the largest prime factor of n.
2
1, 3, 5, 7, 8, 9, 13, 15, 18, 19, 21, 23, 25, 27, 28, 31, 32, 34, 35, 38, 39, 41, 43, 44, 47, 48, 50, 53, 55, 57, 58, 60, 64, 65, 68, 70, 73, 75, 76, 77, 78, 80, 81, 83, 86, 87, 89, 91, 93, 96, 99, 100, 105, 107, 109, 111, 112, 114, 115, 117, 119, 123, 125
OFFSET
1,2
LINKS
EXAMPLE
8 is in the sequence because 8^2+1 = 5*13 and 9^2+1 = 2*41 => 13 < 41.
MATHEMATICA
f[n_]:=FactorInteger[n^2+1][[-1, 1]]; Select[Range[125], f[#]<f[#+1]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jan 23 2012
STATUS
approved