A176550 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A176550

Numbers k such that (k-th odd semiprime)/(j-th prime) is prime and ((k+1)-th odd semiprime)/((j+1)-th prime) is prime for some j.

1, 2, 3, 5, 9, 11, 18, 20, 21, 22, 24, 29, 34, 35, 42, 43, 57, 61, 74, 79, 81, 95, 101, 102, 111, 112, 118, 120, 123, 128, 136, 151, 153, 154, 163, 166, 167, 170, 173, 177, 190, 194, 195, 198, 199, 203, 205, 208, 212, 213, 239, 242, 245, 263, 267, 271, 278, 283

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..58.

MAPLE

A046315 := proc(n) option remember; if n = 1 then 9; else for a from procname(n-1)+2 by 2 do if numtheory[bigomega](a) = 2 then return a; end if; end do: end if; end proc:

A020639 := proc(n) numtheory[factorset](n) ; min(op(%)) ; end proc:

isA176550 := proc(n) os := A046315(n) ; p := A020639(os) ; q := os/p ; ( A046315(n+1) mod nextprime(p) ) = 0 or (A046315(n+1) mod nextprime(q) = 0 ) ; end proc:

for n from 1 to 300 do if isA176550(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, May 30 2010

CROSSREFS

Cf. A046315, A084126, A084127, A176484.

Sequence in context: A329327 A329357 A101737 * A364059 A293036 A214125

Adjacent sequences: A176547 A176548 A176549 * A176551 A176552 A176553

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Apr 20 2010

EXTENSIONS

Corrected (39 removed, 43 inserted) and extended by R. J. Mathar, May 30 2010

STATUS

approved