login
A087713
Greatest prime factor of the product of the neighbors of the n-th prime.
1
3, 2, 3, 3, 5, 7, 3, 5, 11, 7, 5, 19, 7, 11, 23, 13, 29, 31, 17, 7, 37, 13, 41, 11, 7, 17, 17, 53, 11, 19, 7, 13, 23, 23, 37, 19, 79, 41, 83, 43, 89, 13, 19, 97, 11, 11, 53, 37, 113, 23, 29, 17, 11, 7, 43, 131, 67, 17, 139, 47, 71, 73, 17, 31, 157, 79, 83, 13, 173, 29, 59
OFFSET
1,1
COMMENTS
a(n) = A006530((A000040(n)-1)*(A000040(n)+1)) = A006530(A006093(n)*A008864(n)) = A006530(A084920(n)).
Apparently a(n) = A024710(n) for n>4. - Georg Fischer, Oct 06 2018
LINKS
EXAMPLE
a(10) = A006530(A000040(10)^2 - 1) = A006530(29*29-1) =
A006530(840) = A006530(7*5*3*2^3) = 7.
MATHEMATICA
FactorInteger[#][[-1, 1]]&/@((#-1)(#+1)&/@Prime[Range[80]]) (* Harvey P. Dale, Oct 26 2019 *)
PROG
(Haskell)
a087713 = a006530 . a084920 -- Reinhard Zumkeller, Aug 27 2013
CROSSREFS
Sequence in context: A125748 A058680 A070544 * A089319 A140396 A117231
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 28 2003
EXTENSIONS
Definition clarified by Harvey P. Dale, Oct 26 2019
STATUS
approved