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%I #10 Feb 03 2019 12:24:39
%S 1,2,4,6,12,18,24,30,42,60,72,102,108,138,150,168,180,192,198,228,240,
%T 270,282,312,348,420,432,462,522,570,600,618,642,660,810,822,828,858,
%U 882,1020,1032,1050,1062,1092,1152,1230,1278,1290,1302,1320,1368,1428
%N a(1)=1. a(n) = the smallest integer > a(n-1) where both a(n)-1 and a(n)+1 are coprime to all earlier terms of the sequence.
%C Every term from a(4) on is a multiple of 6.
%p A175305 := proc(n) option remember ; local wrks ; if n = 1 then 1; else for a from procname(n-1)+1 do wrks := true; for i from 1 to n-1 do if gcd(a-1,procname(i)) <> 1 or gcd(a+1,procname(i)) <> 1 then wrks := false; end if; end do: if wrks then return a; end if; end do: end if; end proc: seq(A175305(n),n=1..80) ; # _R. J. Mathar_, Apr 15 2010
%K nonn
%O 1,2
%A _Leroy Quet_, Apr 11 2010
%E More terms from _R. J. Mathar_, Apr 15 2010
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