This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A002338 x such that p = (x^2 + 27*y^2)/4, where p is the n-th prime of the form 3k+1. (Formerly M3754 N1531) 2
 1, 5, 7, 4, 11, 8, 1, 5, 7, 17, 19, 13, 2, 20, 23, 19, 14, 25, 7, 23, 11, 13, 28, 22, 17, 29, 26, 32, 16, 35, 1, 5, 37, 35, 13, 29, 34, 31, 19, 2, 28, 10, 23, 25, 32, 43, 29, 1, 31, 11, 26, 49, 47, 17, 43, 40, 49, 37, 8, 53, 44, 50, 16, 41, 29, 49, 31, 56, 5, 7, 35, 13, 59, 47, 19, 52, 61, 41, 61, 10, 43, 14, 53, 59, 64, 65, 62, 55, 22, 65, 35, 67, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A123489 is a signed version. - Michael Somos, Aug 27 2012 REFERENCES A. J. C. Cunningham, Quadratic Partitions. Hodgson, London, 1904, p. 1. B. Engquist and Wilfried Schmid, Mathematics Unlimited - 2001 and Beyond, Chapter on Error-correcting codes and curves over finite fields, see pp. 1118-1119. [From Neven Juric, Oct 16 2008.] D. H. Lehmer, Guide to Tables in the Theory of Numbers. Bulletin No. 105, National Research Council, Washington, DC, 1941, p. 55. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Ruperto Corso, Table of n, a(n) for n = 1..1000 A. J. C. Cunningham, Quadratic Partitions, Hodgson, London, 1904 [Annotated scans of selected pages] S. R. Finch, Powers of Euler's q-Series, (arXiv:math.NT/0701251). PROG (PARI) forprime(p=2, 10000, for(x=1, floor(2*sqrt(p)), px=4*p-x^2; if(px%27==0, if(issquare(px/27, &y), print1(x", "))))) /* Ruperto Corso, Dec 14 2011 */ CROSSREFS Cf. A002339, A123489. Sequence in context: A096437 A096458 A123489 * A226021 A242059 A178668 Adjacent sequences:  A002335 A002336 A002337 * A002339 A002340 A002341 KEYWORD nonn AUTHOR EXTENSIONS Corrected and extended by Ruperto Corso, Dec 14 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.