A178380 The greatest common prime divisor of n, A000032(n)-1 and A001608(n), or 1 if no such greatest common divisor exists.
2, 3, 2, 5, 1, 7, 2, 3, 1, 11, 1, 13, 1, 1, 2, 17, 1, 19, 1, 1, 2, 23, 1, 5, 1, 3, 1, 29, 1, 31, 2, 1, 1, 1, 1, 37, 1, 1, 1, 41, 1, 43, 2, 1, 2, 47, 1, 7, 2, 1, 1, 53, 1, 1, 1, 1, 2, 59, 1, 61, 1, 1, 2, 1, 1, 67, 1, 1, 1, 71, 1, 73, 2, 1, 1, 1, 1, 79, 1, 3, 1, 83, 1, 1, 2, 1, 2, 89, 1
Offset: 2
Keywords
Programs
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Maple
A000032 := proc(n) ((1+sqrt(5))/2)^n + ((1-sqrt(5))/2)^n ; expand(%) ; end proc: A001608 := proc(n) coeftayl( (3-x^2)/(1-x^2-x^3),x=0,n) ; end proc: A178380 := proc(n) local g; g := igcd(n, A000032(n)-1, A001608(n)) ; if g = 1 then 1; else numtheory[factorset](%) ; max( op(%)) ; end if; end proc: seq(A178380(n),n=2..90) ; # R. J. Mathar, Aug 08 2010
Extensions
More terms from R. J. Mathar, Aug 08 2010
Comments