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A013806
a(n) = 17^(4*n+1).
2
17, 1419857, 118587876497, 9904578032905937, 827240261886336764177, 69091933913008732880827217, 5770627412348402378939569991057, 481968572106750915091411825223071697, 40254497110927943179349807054456171205137
OFFSET
0,1
COMMENTS
As phi(a(n)) = (2*17^n)^4 is a perfect biquadrate (where phi is the Euler totient A000010), this is a subsequence of A078164 and A307690. - Bernard Schott, Mar 29 2022
FORMULA
a(0)=17, a(n)=83521*a(n-1). - Harvey P. Dale, May 21 2013
Sum_{n>=0} 1/a(n) = 4913/83520. - Bernard Schott, Mar 29 2022
Sum_{n>=0} (-1)^n/a(n) = 4913/83522. - Bernard Schott, Apr 08 2022
MATHEMATICA
17^(4Range[0, 10]+1) (* or *) NestList[83521#&, 17, 20] (* Harvey P. Dale, May 21 2013 *)
PROG
(Magma) [17^(4*n+1): n in [0..15]]; // Vincenzo Librandi, Jul 06 2011
CROSSREFS
Intersection of A001026 and A078164.
Sequence in context: A130653 A125039 A125041 * A147671 A104536 A178716
KEYWORD
nonn,easy
STATUS
approved