login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A144652 Triangle, read by rows, where T(m,n) = floor((2mn+m+n)/2) with m >= n >= 1. 1
2, 3, 6, 5, 8, 12, 6, 11, 15, 20, 8, 13, 19, 24, 30, 9, 16, 22, 29, 35, 42, 11, 18, 26, 33, 41, 48, 56, 12, 21, 29, 38, 46, 55, 63, 72, 14, 23, 33, 42, 52, 61, 71, 80, 90, 15, 26, 36, 47, 57, 68, 78, 89, 99, 110, 17, 28, 40, 51, 63, 74, 86, 97, 109, 120, 132, 18, 31, 43, 56, 68 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

From Vincenzo Librandi, Nov 16 2012: (Start)

First column:  A007494(n+1);

second column: A047219(n+2);

third column:  A047383(n+3);

fourth column: A193910(n+4).

Conjecture: If h does not belong to the sequence, then 4*h+1 is prime. (End)

LINKS

Vincenzo Librandi, Rows n = 1..100, flattened

EXAMPLE

Triangle begins:

2;

3,  6;

5,  8,  12;

6,  11, 15, 20;

8,  13, 19, 24, 30;

9,  16, 22, 29, 35, 42;

11, 18, 26, 33, 41, 48, 56; etc.

MATHEMATICA

Flatten[Table[Floor[(2*n*m + m + n)/2], {n, 1, 20}, {m, n}]] (* Vincenzo Librandi, Nov 16 2012 *)

PROG

(MAGMA) [Floor((2*n*k+n+k)/2): k in [1..n], n in [1..11]]; // Vincenzo Librandi, Nov 16 2012

CROSSREFS

Cf. A007494, A047219, A047383, A193910.

Sequence in context: A276081 A329564 A257011 * A035493 A070038 A328638

Adjacent sequences:  A144649 A144650 A144651 * A144653 A144654 A144655

KEYWORD

nonn,tabl,easy

AUTHOR

Vincenzo Librandi, Jan 27 2009

EXTENSIONS

Definition edited (specifying m >= n >= 1), and terms recomputed to match definition, as was done with the similar sequence A140869, by Jon E. Schoenfield, Jun 24 2010

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)