The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A002407 Cuban primes: primes which are the difference of two consecutive cubes. (Formerly M4363 N1828) 30
 7, 19, 37, 61, 127, 271, 331, 397, 547, 631, 919, 1657, 1801, 1951, 2269, 2437, 2791, 3169, 3571, 4219, 4447, 5167, 5419, 6211, 7057, 7351, 8269, 9241, 10267, 11719, 12097, 13267, 13669, 16651, 19441, 19927, 22447, 23497, 24571, 25117, 26227 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes of the form p = (x^3 - y^3)/(x - y) where x=y+1. See A007645 for generalization. I first saw the name "cuban prime" in Cunningham (1923). Values of x are in A002504. - N. J. A. Sloane, Jan 29 2013 Prime hex numbers (cf. A003215). Equivalently, primes of the form p=1+3k(k+1) (and then k=floor(sqrt(p/3))). Also: primes p such that n^2(p+n) is a cube for some n>0. - M. F. Hasler, Nov 28 2007 Primes p such that 4p = 1+3n^2 for some integer n. - Michael Somos, Sep 15 2005 The cuban primes may be generated from the hexagonal centered numbers by eliminating all the items that may be expressed as 36*i*j + 6*i + 6*j + 1 with i,j integers. - Giacomo Fecondo, Mar 13 2009, Mar 17 2009 This sequence is believed to be infinite. - N. J. A. Sloane, May 07 2020 REFERENCES Allan Joseph Champneys Cunningham, On quasi-Mersennian numbers, Mess. Math., 41 (1912), 119-146. Allan Joseph Champneys Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929; see Vol. 1, pp. 245-259. J.-M. De Koninck & A. Mercier, 1001 Problèmes en Théorie Classique des Nombres, Problem 241 pp. 39; 179, Ellipses Paris 2004. 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 T. D. Noe, Table of n, a(n) for n = 1..1000 A. J. C. Cunningham, On quasi-Mersennian numbers, Mess. Math., 41 (1912), 119-146. [Annotated scan of page 144 only] A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929. [Annotated scans of a few pages from Volumes 1 and 2] R. K. Guy, Letter to N. J. A. Sloane, 1987 G. L. Honaker, Jr., Prime curio for 127 Project Euler, Problem 131: Prime cube partnership. Eric Weisstein's World of Mathematics, Cuban Prime Wikipedia, Cuban prime FORMULA a(n) = 6*A000217(A111251(n)) + 1. - Christopher Hohl, Jul 01 2019 EXAMPLE a(1) = 7 = 1+3k(k+1) (with k=1) is the smallest prime of this form. a(10^5) = 1792617147127 since this is the 100000th prime of this form. MATHEMATICA lst={}; Do[If[PrimeQ[p=(n+1)^3-n^3], (*Print[p]; *)AppendTo[lst, p]], {n, 10^2}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 21 2008 *) Select[Table[3x^2+3x+1, {x, 100}], PrimeQ] (* or *) Select[Last[#]- First[#]&/@ Partition[Range^3, 2, 1], PrimeQ] (* Harvey P. Dale, Mar 10 2012 *) Select[Differences[Range^3], PrimeQ] (* Harvey P. Dale, Jan 19 2020 *) PROG (PARI) {a(n)= local(m, c); if(n<1, 0, c=0; m=1; while( c

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

Last modified April 21 23:52 EDT 2021. Contains 343156 sequences. (Running on oeis4.)