OFFSET
1,1
COMMENTS
Also numbers n such that mu(n^2+1) = mu((n+1)^2+1)=0, where mu is the Moebius-function (A008683).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
117 is in the sequence because 117^2+1 = 2*5*37^2 and 118^2+1 = 5^2*557.
MAPLE
with(numtheory):for n from 1 to 10000 do :x:=n^2+1:y:=(n+1)^2+1:if issqrfree(x)=false and issqrfree(y)=false then printf(`%d, `, n):else fi:od:
MATHEMATICA
Select[ Range[2, 10000], Max[ Transpose[ FactorInteger[ #^2+1 ]] [[2]]] > 1 && Max[ Transpose[ FactorInteger[ (#+1)^2 + 1]] [[2]]] > 1 &]
PROG
(Magma) A002522:=func<m | m^2+1>; [n: n in [1..10^4]| not IsSquarefree(A002522(n)) and not IsSquarefree(A002522(n+1))]; // Bruno Berselli, Oct 15 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Oct 12 2012
STATUS
approved