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.

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

G. C. Greubel, Table of n, a(n) for n = 1..1000

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

Cf. A002522, A070089, A006530, A070087, A185002.

Sequence in context: A191257 A120212 A093670 * A175144 A183054 A188569

Adjacent sequences: A185008 A185009 A185010 * A185012 A185013 A185014

Keyword

nonn

Author

Michel Lagneau, Jan 23 2012

Status

approved