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 A130062 Nonprime numbers k such that k divides 3^((k+1)/2) - 2^((k+1)/2) - 1. 5
 1, 21, 49, 105, 1729, 2465, 2877, 7305, 10585, 15841, 31021, 31621, 32041, 41041, 46657, 52633, 54145, 75361, 83333, 115921, 126217, 162401, 172081, 211141, 282133, 284649, 294409, 334153, 383161, 399001, 417241, 449065, 488881, 530881 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The perfect squares in listed terms are a(1) = 1, a(3) = 49 = 7^2, a(13) = 32041 = 179^2 and a(29) = 383161 = 619^2. Note that primes {7,179,619} are the terms of A130060 or primes in A127074. LINKS Amiram Eldar, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[ 2*Range[100000]-1, !PrimeQ[ # ] && Mod[ PowerMod[3, (#+1)/2, # ] - PowerMod[2, (#+1)/2, # ] - 1, # ] == 0 & ] CROSSREFS Cf. A097934 (primes p that divide 3^((p-1)/2) - 2^((p-1)/2). Cf. A038876 (primes p such that 6 is a square mod p. Cf. A127071, A127072, A127073, A127074. Cf. A130058, A130059, A130061, A130063, A130060, A127074. Sequence in context: A347372 A141556 A147281 * A153441 A357679 A235884 Adjacent sequences: A130059 A130060 A130061 * A130063 A130064 A130065 KEYWORD nonn AUTHOR Alexander Adamchuk, May 05 2007 EXTENSIONS More terms from Ryan Propper, Jan 07 2008 STATUS approved

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Last modified September 18 11:24 EDT 2024. Contains 376000 sequences. (Running on oeis4.)