login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A125602 Prime centered triangular numbers. 5
19, 31, 109, 199, 409, 571, 631, 829, 1489, 1999, 2341, 2971, 3529, 4621, 4789, 7039, 7669, 8779, 9721, 10459, 10711, 13681, 14851, 16069, 16381, 17659, 20011, 20359, 23251, 25939, 27541, 29191, 29611, 31321, 34429, 36739, 40099, 40591, 42589 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Or prime terms in A005448, or primes of the form 3n(n-1)/2 + 1.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

lst={}; Do[If[PrimeQ[p=3n(n-1)/2+1], (*Print[p]; *)AppendTo[lst, p]], {n, 10^3}]; lst [From Vladimir Joseph Stephan Orlovsky, Aug 21 2008]

PROG

(MAGMA) [a: n in [0..200] | IsPrime(a) where a is  (3*n^2 - 3*n + 2) div 2]; // Vincenzo Librandi, Mar 22 2013

CROSSREFS

Cf. A005448, A125603.

Sequence in context: A243450 A237418 A240126 * A139847 A087764 A146691

Adjacent sequences:  A125599 A125600 A125601 * A125603 A125604 A125605

KEYWORD

nonn,easy

AUTHOR

Zak Seidov, Nov 27 2006

STATUS

approved

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

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

Last modified December 21 08:26 EST 2014. Contains 252299 sequences.