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A179273 Primes in A179272. 1
2, 5, 7, 11, 19, 23, 29, 41, 47, 71, 79, 89, 109, 131, 167, 181, 223, 239, 271, 359, 379, 419, 439, 461, 599, 701, 727, 811, 839, 929, 991, 1087, 1223, 1259, 1367, 1481, 1559, 1721, 1847, 1979, 2069, 2161, 2207, 2351, 2399, 2549, 2861, 2969, 3023, 3079, 3191 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes of form floor(((n^2)/4) - (n/2) - 1). Primes in sharp upper bound on Rosgen overlap number n-vertex graph with n => 14, formula abused here for nonnegative integers. There seem to be more primes (29) through n = 60 of floor(((n^2)/4) - (n/2) - 1) than one might expect. What fraction through n = 1000 are prime?

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Daniel W. Cranston, Nitish Korula, Timothy D. LeSaulnier, Kevin Milans, Christopher Stocker, Jennifer Vandenbussche, Douglas B. West, Overlap Number of Graphs, Jul 06, 2010.

EXAMPLE

a(1) = floor(((5^2)/4) - (5/2) - 1) = floor(16/4 - 5/2 - 1) = floor(11/4) = 2.

a(2) = floor(((6^2)/4) - (6/2) - 1) = floor(36/4 - 6/2 - 1) = floor(5) = 5.

MATHEMATICA

Select[Table[Floor[n^2/4-n/2-1], {n, 5, 200}], PrimeQ] (* Harvey P. Dale, Oct 12 2012 *)

CROSSREFS

Cf. A000040, A179272.

Sequence in context: A162491 A152216 A045350 * A251964 A045351 A051645

Adjacent sequences:  A179270 A179271 A179272 * A179274 A179275 A179276

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Jul 07 2010

EXTENSIONS

More terms from R. J. Mathar, Oct 15 2010

STATUS

approved

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Last modified June 20 01:09 EDT 2021. Contains 345154 sequences. (Running on oeis4.)