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 A135546 Let p be the n-th prime and let g be the order of 2 mod p (see A014664). Then if g is even, a(n) = p*(2^(g/2) - 1), otherwise a(n) = 2^g - 1. 2
 3, 15, 7, 341, 819, 255, 9709, 2047, 475107, 31, 9699291, 41943, 5461, 8388607, 3556769739, 31675383749, 65498251203, 575525617597, 34359738367, 511, 549755813887, 182518930210733, 2047, 1627389855, 113715890591104923, 2251799813685247, 963770320257286037 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Karpenkov asks how often is it the case that if p is the n-th prime (n >= 2) then A038553(p) = a(n)? The first failure is at p = 37. Is it true that a(n) is always divisible by A038553(p)? REFERENCES O. N. Karpenkov, On examples of difference operators ..., Funct. Anal. Other Math., 1 (2006), 175-180. [The function q(n)] LINKS N. J. A. Sloane, Table of n, a(n) for n = 2..1000 MAPLE (First load the b-file for A014664 as the array b1.) a := proc(i) local p, g; p:=ithprime(i); g:=b1[i-1]; if g mod 2 = 0 then p*(2^(g/2)-1) else 2^g-1; fi; end; CROSSREFS Cf. A038553, A014664. Sequence in context: A066832 A102777 A102531 * A138006 A256557 A145179 Adjacent sequences:  A135543 A135544 A135545 * A135547 A135548 A135549 KEYWORD nonn AUTHOR N. J. A. Sloane, Feb 24 2008 STATUS approved

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Last modified October 17 22:16 EDT 2019. Contains 328134 sequences. (Running on oeis4.)