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 A199401 Decimal expansion of constant Product_{p>=3} (1 - (-1)^((p-1)/2)/(p-1)). Hardy-Littlewood constant of x^2 + 1. 4
 1, 3, 7, 2, 8, 1, 3, 4, 6, 2, 8, 1, 8, 2, 4, 6, 0, 0, 9, 1, 1, 2, 1, 9, 2, 6, 9, 6, 7, 2, 7, 0, 1, 8, 8, 6, 8, 1, 7, 8, 3, 3, 3, 1, 0, 1, 2, 5, 5, 7, 5, 9, 5, 5, 7, 9, 3, 6, 2, 3, 4, 1, 4, 7, 3, 2, 7, 8, 4, 2, 2, 2, 6, 7, 1, 7, 3, 7, 0, 2, 3, 1, 7, 2, 7, 7, 1 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Arises in studying A002496. The constant is Product_{primes p} (1-chi(p)/(p-1)) where chi is the Dirichlet character A101455. Its Euler expansion is (1/(L(m=4,r=2,s=1)* zeta(m=4,n=3,s=2)) *Product_{s>=2} zeta(m=4,n=1,s)^gamma(s), where L and zeta are the functions tabulated in arXiv:1008.2547 and gamma is the sequence A001037. In particular L(m=4,r=2,s=1) = A003881 and zeta(m=4,n=1,s=2)=A175647. - R. J. Mathar, Nov 29 2011 REFERENCES G. H. Hardy and J. E. Littlewood. Some problems of Partitio Numerorum III: On the expression of a number as a sum of primes. Acta Mathematica, 44 (1922). 1-70. See Section 5.41. LINKS T. Amdeberhan, L. A. Median, V. H. Moll, Arithmetical properties of a sequence arising from an arctangent sum, J. Numb. Theory 128 (2008) 1807-1846, eq. (1.10). Karim Belabas, Henri Cohen, Computation of the Hardy-Littlewood constant for quadratic polynomials, PARI/GP script, 2020. N. A. Carella, The Euler Polynomial Prime Values Problem, arXiv:1912.05923 [math.GM], 2019. Henri Cohen, High-precision computation of Hardy-Littlewood constants, (1998). [pdf copy, with permission] Richard J. Mathar, Table of Dirichlet L-Series and Prime Zeta Modulo Functions for Small Moduli, arXiv:1008.2547 [math.NT], 2010-2015. Marek Wolf, Search for primes of the form m^2+1, arXiv:0803.1456 [math.NT], 2008-2010. EXAMPLE 1.372813462818246009112192696727... PROG (PARI) See Belabas, Cohen link. Run as HardyLittlewood2(x^2+1) after setting the required precision. CROSSREFS Cf. A002496. Cf. A001037, A003881, A083844, A175647, A221712, A331942. Equals 2*constant given by A331941. Sequence in context: A279341 A254155 A211342 * A261573 A159759 A243964 Adjacent sequences:  A199398 A199399 A199400 * A199402 A199403 A199404 KEYWORD nonn,cons AUTHOR N. J. A. Sloane, Nov 05 2011 EXTENSIONS Extended title, a(30) and beyond from Hugo Pfoertner, Feb 16 2020 STATUS approved

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