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A235540
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Composite numbers m such that (4^m - 2^m + 8*m^2 - 2) / (2*m*(2*m + 1)) is integral.
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3
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243, 891, 1539, 2211, 2511, 13203, 19683, 87723, 92583, 150851, 202851, 292923, 321651, 399771, 412623, 452051, 1325843, 1330551, 1441091, 1566891, 3026871, 4422231, 4954851, 4974971, 5016191, 5845851, 5971239, 6773139, 11050911, 11720511, 12602871, 14666751
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OFFSET
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1,1
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COMMENTS
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Nonprimes in A158034.
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LINKS
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Chai Wah Wu, Table of n, a(n) for n = 1..89
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MATHEMATICA
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Select[Range[10^6], CompositeQ[#]&&IntegerQ[(4^#-2^#+8#^2-2)/(2#(2#+1))]&] (* Harvey P. Dale, Nov 17 2014 *)
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PROG
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(Haskell)
a235540 n = a235540_list !! (n-1)
a235540_list = filter ((== 0) . a010051') a158034_list
(Python)
from gmpy2 import is_prime, powmod, t_mod
A235540_list = []
for i in range(1, 10**9+1):
....if not is_prime(i):
........d = 2*i*(2*i+1)
........n = t_mod(powmod(4, i, d)-powmod(2, i, d)+8*i*i-2, d)
........if not n:
............A235540_list.append(i) # Chai Wah Wu, Dec 02 2014
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CROSSREFS
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Cf. A158034, A010051, A002808.
Sequence in context: A331613 A255626 A205049 * A219132 A232285 A113335
Adjacent sequences: A235537 A235538 A235539 * A235541 A235542 A235543
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller, Jan 12 2014
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EXTENSIONS
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New definition from Reinhard Zumkeller, Nov 17 2014. Thanks to Harvey P. Dale, who observed that the original definition was wrong.
More terms from Harvey P. Dale, Nov 17 2014
More terms from Chai Wah Wu, Dec 02 2014
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STATUS
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approved
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