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 A139474 a(n) = ((2*sqrt(2) + 3)^(2^(prime(n) - 1) - 1) - (3 - 2*sqrt(2))^(2^(prime(n) - 1) - 1))/(4*sqrt(2)). 5
 1, 35, 53789260175, 300027707381709879256191290532493317737977820735 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next term a(5) has 783 decimal digits. Conjecture of Kenneth J Ramsey from May 16 2006 (see A001109): a(n) is divisible by 2^prime(n)-1 if and only 2^prime(n)-1 is a Mersenne prime. LINKS Table of n, a(n) for n=1..4. MATHEMATICA Table[Expand[((2*Sqrt[2] + 3)^(2^(Prime[n] - 1) - 1) - (3 - 2*Sqrt[2])^(2^(Prime[n] - 1) - 1))/(4*Sqrt[2])], {n, 1, 10}] CROSSREFS Cf. A001109, A139474, A139475, A139476. Sequence in context: A126029 A107736 A261121 * A240129 A023929 A010113 Adjacent sequences: A139471 A139472 A139473 * A139475 A139476 A139477 KEYWORD nonn AUTHOR Artur Jasinski, Apr 22 2008 STATUS approved

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Last modified July 14 02:38 EDT 2024. Contains 374291 sequences. (Running on oeis4.)