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
Offset: 1
Keywords
Programs
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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
Extensions
Corrected (39 removed, 43 inserted) and extended by R. J. Mathar, May 30 2010