This site is supported by donations to The OEIS Foundation.

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A090562 Primes of the form 5k^2 + 5k + 1 13
 11, 31, 61, 101, 151, 211, 281, 661, 911, 1051, 1201, 1361, 1531, 1901, 2311, 2531, 3001, 3251, 3511, 4651, 5281, 6301, 6661, 7411, 9461, 9901, 12251, 13781, 14851, 15401, 18301, 18911, 19531, 20161, 22111, 24151, 24851, 25561, 27011, 27751 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Or, primes obtained as a concatenation of a triangular number and 1. Centered decagonal primes. - Paul Muljadi, Oct 04 2005 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..5000 Wikipedia, Centered decagonal number. MATHEMATICA Select[5(#^2 - #) + 1 & /@ Range[75], PrimeQ[ # ] &] (* Robert G. Wilson v *) PROG (MAGMA) [a: n in [0..100] | IsPrime(a) where a is 5*n^2 + 5*n + 1]; // Vincenzo Librandi, Dec 13 2011 CROSSREFS Cf. A090563. Sequence in context: A202007 A125239 A062786 * A174244 A136061 A090233 Adjacent sequences:  A090559 A090560 A090561 * A090563 A090564 A090565 KEYWORD easy,nonn AUTHOR Amarnath Murthy, Dec 11 2003 EXTENSIONS Edited and extended by Robert G. Wilson v, Oct 10 2005 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.