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%I #24 Aug 15 2021 10:07:22
%S 3,8,3,8,3
%N Lengths of rows in A124570.
%C This sequence is to A124570 as A123556 is to A124064.
%C a(n) is at most A053669(n)^2, with equality if and only if A053669(n)^2 is the first semiprime in the corresponding arithmetic progression. - _Charlie Neder_, Jan 10 2019
%C By subsampling a given arithmetic progression with k terms and distance d one may generate an arithmetic progression of a larger distance d*b, b=1,2,3...., with 1+(k-1)/b terms: a(b*n) >= 1+floor( (a(n)-1)/b ), b=1,2,3..... - _R. J. Mathar_, Aug 02 2021
%C 18 <= a(6) <= 24. - _Jinyuan Wang_, Aug 06 2021
%C a(12) >= 17. a(18) >= 18. a(24) >= 18. a(30) >= 21. a(36) >= 19. a(42) >= 20. a(6006) >= 24 (starting 652744562555081). _Hugo van der Sanden_, Aug 14 2021
%Y Cf. A001358, A123556, A124064, A124570, A091016 (for n=6).
%K nonn,hard,more
%O 1,1
%A _Jonathan Vos Post_, Nov 15 2006
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