A060954 Largest prime factor of 10*n + 1.

11, 7, 31, 41, 17, 61, 71, 3, 13, 101, 37, 11, 131, 47, 151, 23, 19, 181, 191, 67, 211, 17, 11, 241, 251, 29, 271, 281, 97, 43, 311, 107, 331, 31, 13, 19, 53, 127, 23, 401, 137, 421, 431, 7, 41, 461, 157, 37, 491, 167, 73, 521, 59, 541, 29, 17, 571, 83, 197, 601, 47

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

László Tóth, Counting solutions of quadratic congruences in several variables revisited, arXiv preprint arXiv:1404.4214 [math.NT], 2014.

László Tóth, Counting Solutions of Quadratic Congruences in Several Variables Revisited, J. Int. Seq. 17 (2014), # 14.11.6.

Example

21 = 3*7, so a(2) = 7.

Mathematica

Table[First[Last[FactorInteger[10n + 1]]], {n, 1, 80}]

Prog

(PARI) { for (n=1, 1000, f=factor(10*n + 1)~; write("b060954.txt", n, " ", f[1, length(f)]); ) } \\ Harry J. Smith, Jul 19 2009
(Python)
from sympy import factorint
def a(n): return max(factorint(10*n+1))
print([a(n) for n in range(1, 62)]) # Michael S. Branicky, Nov 07 2021

Crossrefs

Sequence in context: A206419 A250032 A305447 * A350214 A038321 A355299

Adjacent sequences: A060951 A060952 A060953 * A060955 A060956 A060957

Keyword

nonn

Author

J. Lowell, May 08 2001

Extensions

More terms from Reiner Martin, Jul 07 2001

Status

approved