

A181449


Numbers n such that 7 is the largest prime factor of n^2  1.


2



6, 8, 13, 15, 29, 41, 55, 71, 97, 99, 127, 244, 251, 449, 4801, 8749
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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(4) = 8749; primepi(7) = 4.


LINKS

Table of n, a(n) for n=1..16.


MATHEMATICA

Select[Range[9000], FactorInteger[#^21][[1, 1]]==7&]


PROG

(MAGMA) [ n: n in [2..9000]  m eq 7 where m is D[#D] where D is PrimeDivisors(n^21) ]; // Klaus Brockhaus, Feb 17 2011
(PARI) is(n)=n=n^21; forprime(p=2, 5, n/=p^valuation(n, p)); n>1 && 7^valuation(n, 7)==n \\ Charles R Greathouse IV, Jul 01 2013


CROSSREFS

Cf. A175607, A181447, A181448, A181450A181470, A181568.
Sequence in context: A285678 A027706 A047336 * A315874 A315875 A315876
Adjacent sequences: A181446 A181447 A181448 * A181450 A181451 A181452


KEYWORD

fini,full,nonn


AUTHOR

Artur Jasinski, Oct 21 2010


STATUS

approved



