

A181448


Numbers n such that 5 is the largest prime factor of n^2  1.


2




OFFSET

1,1


COMMENTS

Sequence is finite and complete, for proof see A175607.
Search for terms can be restricted to the range from 2 to A175607(3) = 161; primepi(5) = 3.


LINKS

Table of n, a(n) for n=1..8.


MATHEMATICA

Select[Range[200], FactorInteger[#^21][[1, 1]]==5&]


PROG

(MAGMA) [ n: n in [2..200]  m eq 5 where m is D[#D] where D is PrimeDivisors(n^21) ]; // Klaus Brockhaus, Feb 17 2011
(PARI) is(n)=n=n^21; n>>=valuation(n, 2); n/=3^valuation(n, 3); n>1 && 5^valuation(n, 5)==n \\ Charles R Greathouse IV, Jul 01 2013


CROSSREFS

Cf. A175607, A181447, A181449A181470, A181568.
Sequence in context: A312843 A206523 A312844 * A312845 A312846 A182244
Adjacent sequences: A181445 A181446 A181447 * A181449 A181450 A181451


KEYWORD

fini,full,nonn


AUTHOR

Artur Jasinski, Oct 21 2010


STATUS

approved



