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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A263676 Numbers that are both interprime and oblong. 2
6, 12, 30, 42, 56, 72, 240, 342, 420, 462, 506, 552, 600, 650, 870, 1056, 1190, 1482, 1722, 1806, 2550, 2652, 2970, 3540, 4422, 6320, 7140, 8010, 10302, 12656, 13572, 14042, 17292, 18360, 19182, 19460, 20022, 22952, 23562, 24180, 27060, 29070, 29756, 31152, 33306, 35156, 35532, 39006 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A024675 and A002378. - Omar E. Pol, Oct 24 2015

Lesser of consecutive primes is in the sequence A242383.

LINKS

Table of n, a(n) for n=1..48.

Eric Weisstein's World of Mathematics, Interprime

Eric Weisstein's World of Mathematics, Pronic Number

EXAMPLE

342 is in this sequence because 342 = 18*19 is oblong, and 342 = (337 + 347)/2, with 337 and 347 consecutive primes.

MATHEMATICA

lim = 40000; Intersection[Plus @@@ Partition[Table[Prime@ n, {n, 2, PrimePi@ lim}], 2, 1]/2, Table[n (n + 1), {n, 0, lim}]] (* Michael De Vlieger, Nov 18 2015, after Clark Kimberling at A024675 and Robert G. Wilson v at A002378 *)

PROG

(PARI) {for(i=1, 500, n=i*(i+1); if(n==(precprime(n-1)+nextprime(n+1))/2, print1(n, ", ")))}

CROSSREFS

Cf. A002378, A024675, A075190, A075277, A075296, A078443, A130178, A242383, A263674, A263675.

Sequence in context: A143272 A153877 A229491 * A083494 A126857 A161348

Adjacent sequences:  A263673 A263674 A263675 * A263677 A263678 A263679

KEYWORD

nonn,easy

AUTHOR

Antonio Roldán, Oct 23 2015

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 21 19:29 EDT 2018. Contains 315260 sequences. (Running on oeis4.)