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

 

Logo

Many excellent designs for a new banner were submitted. We will use the best of them in rotation.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A109406 Numbers n such that (sp(n)+sp(n+1)+sp(n+2))/3 is integer, sp(n) = n-th semiprime. 0
3, 4, 9, 10, 11, 14, 20, 28, 29, 32, 34, 40, 43, 44, 45, 46, 50, 53, 58, 59, 61, 62, 63, 68, 69, 72, 74, 80, 83, 86, 89, 95, 99, 100, 101, 105, 107, 109, 111, 112, 115, 116, 118, 119, 121, 123, 127, 129, 130, 131, 132, 136, 137, 140, 144, 145, 150, 151, 152, 153, 155 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

3 is OK because (sp(3)+sp(4)+sp(5))/3=(9+10+14)/3 = 11; sp(n) = n-th semiprime.

PROG

(PARI) lista(nn) = {vec = vector(nn, i, i); sp = select(i->(bigomega(i)==2), vec); for (i = 1, #sp-2, if (((sp[i]+sp[i+1]+sp[i+2]) % 3) == 0, print1(i, ", ")); ); } \\ Michel Marcus, Oct 06 2013

CROSSREFS

Cf. A075541.

Sequence in context: A220695 A079258 A134025 * A178462 A010376 A010388

Adjacent sequences:  A109403 A109404 A109405 * A109407 A109408 A109409

KEYWORD

nonn

AUTHOR

Zak Seidov, Jun 27 2005

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 April 24 19:08 EDT 2014. Contains 240988 sequences.