This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A111051 Numbers n such that 3*n^2 + 1 is prime. 5
 2, 6, 8, 12, 16, 20, 22, 26, 34, 36, 40, 58, 64, 68, 78, 82, 84, 86, 98, 112, 120, 126, 142, 146, 148, 152, 156, 160, 168, 188, 190, 194, 196, 208, 216, 218, 222, 238, 240, 244, 246, 254, 264, 272, 282, 286, 294, 300, 302, 306, 308, 316, 320, 330, 338, 344, 348 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The resulting primes are the generalized cuban primes of the form p = (x^3 - y^3 )/(x - y), x=y+2 (see A002648). - Jani Melik, Jul 18 2007 LINKS Zak Seidov, Table of n, a (n) for n = 1..1000 EXAMPLE a(1)=2 because p = 1+3*2^2 = 13 is prime. a(2)=6 because p = 1+3*6^2 = 109 is prime. a(3)=8 because p = 1+3*8^2 = 193 is prime. If n=98 then (3*n^2) + 1 = 28813 (prime). MAPLE ts_kubpra_ind:=proc(n) local i, tren, ans; ans:=[ ]: for i from 0 to n do tren:=1+3*i^2: if (isprime(tren)='true') then ans:=[ op(ans), i ] fi od: RETURN(ans); end: ts_kubpra_ind(2000); - Jani Melik, Jul 18 2007 CROSSREFS Cf. A002648. Sequence in context: A057656 A084724 A189400 * A077561 A008407 A111224 Adjacent sequences:  A111048 A111049 A111050 * A111052 A111053 A111054 KEYWORD nonn AUTHOR Parthasarathy Nambi, Oct 06 2005 EXTENSIONS More terms from Jani Melik, Jul 18 2007 Edited by N. J. A. Sloane, Sep 28 2007 STATUS approved

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

Content is available under The OEIS End-User License Agreement .