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 A235540 Composite numbers m such that (4^m - 2^m + 8*m^2 - 2) / (2*m*(2*m + 1)) is integral. 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Nonprimes in A158034. LINKS Chai Wah Wu, Table of n, a(n) for n = 1..89 MATHEMATICA Select[Range[10^6], CompositeQ[#]&&IntegerQ[(4^#-2^#+8#^2-2)/(2#(2#+1))]&] (* Harvey P. Dale, Nov 17 2014 *) PROG (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 CROSSREFS Cf. A158034, A010051, A002808. Sequence in context: A331613 A255626 A205049 * A219132 A232285 A113335 Adjacent sequences:  A235537 A235538 A235539 * A235541 A235542 A235543 KEYWORD nonn AUTHOR Reinhard Zumkeller, Jan 12 2014 EXTENSIONS 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 STATUS approved

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Last modified January 27 15:17 EST 2021. Contains 340467 sequences. (Running on oeis4.)