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A066827 a(n) = gcd(2^((n*(n+1)/2)) + 1, 2^n + 1). 1
3, 1, 1, 1, 33, 1, 1, 1, 513, 1, 1, 1, 8193, 1, 1, 1, 131073, 1, 1, 1, 2097153, 1, 1, 1, 33554433, 1, 1, 1, 536870913, 1, 1, 1, 8589934593, 1, 1, 1, 137438953473, 1, 1, 1, 2199023255553, 1, 1, 1, 35184372088833, 1, 1, 1, 562949953421313, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..500

FORMULA

If n is not congruent to 1 mod 4, a(n) = 1. If n is congruent to 1 mod 4, a(n) = 2^n + 1.

G.f.: (-16x^5-2x^2+3x)/(16x^4-1)/(x-1). - Ralf Stephan, Mar 12 2003

PROG

(PARI) { for (n=1, 500, write("b066827.txt", n, " ", gcd(2^((n*(n+1)/2)) + 1, 2^n + 1)) ) } \\ Harry J. Smith, Mar 30 2010

CROSSREFS

Sequence in context: A320412 A286591 A297557 * A016467 A342275 A324049

Adjacent sequences:  A066824 A066825 A066826 * A066828 A066829 A066830

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jan 20 2002

STATUS

approved

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Last modified September 23 17:47 EDT 2021. Contains 347618 sequences. (Running on oeis4.)