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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. 0
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 * A293036 A214125 A275466

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

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Last modified November 24 10:48 EST 2020. Contains 338612 sequences. (Running on oeis4.)